[2] To read the Scriptures publicly; for the proof of which, 1. That the priests and Levites in the Jewish church were trusted with the public reading of the word is proved. 2. That the ministers of the gospel have as ample a charge and commission to dispense the word, as well as other ordinances, as the priests and Levites had under the law, proved, Isa. lxvi. 21. Matt. xxiii. 34. where our Savior entitles the officers of the New Testament, whom he will send forth, by the same names of the teachers of the Old. Which propositions prove, that therefore (the duty being of a moral nature) it follows by just consequence, that the public reading of the scriptures belongs to the pastor's office.

A couple things to note. First, see how the Westminster divines used the OT ecclesiastical and liturgical situation to inform their understanding of the function of the Minister today. Second, if the pastor is called to read the Scriptures publicly, why is this reading so neglected today? And why does everyone but the pastor seem to be the one called on to read Scripture in church?

Continuing with the pastors ministerial duties:
[3] To feed the flock, by preaching of the word, according to which he is to teach, convince, reprove, exhort, and comfort.
[4] To catechize, which is a plain laying down the first principles of the oracles of God, or of the doctrine of Christ, and is a part of preaching.
[5] To dispense other divine mysteries.
[6]To administer the sacraments.
[7] To bless the people from God, Numb. vi. 23, 24, 25, 26. Compared with Rev. i.4, 5, (where the same blessings, and persons from whom they come, are expressly mentioned), Isa. lxvi. 21, where, under the names of Priests and Levites to be continued under the gospel, are meant evangelical pastors, who therefore are by office to bless the people.
[8] To take care of the poor

Once again, pay attention to how the Assembly saw the NT pastorate as the fulfillment, in some sense, of the OT priestly calling. The link between Christian pastors and Hebrew priests is made explicit by Westminster when they summarize the three ordained offices in the Church:

As there were in the Jewish church elders of the people joined with the priests and Levites in the government of the church (2 Chron. 19:8,9,10); so Christ, who hath instituted government, and governors ecclesiastical in the church, hath furnished some in his church, beside the ministers of the word, with gifts for government, and with commission to execute the same when called thereunto, who are to join with the minister in the government of the church (Rom. 12:7,8; 1 Cor. 12:28). Which officers Protestant churches commonly call Elders.

I'm not necessarily saying that this is the best way to explain the connections between the old order and the new situation in the Church. But one should notice that the Protestant tradition can make these links without denying the "priesthood of all believers." A high view of the Ministry does not necessarily mean that one is a Romanist or that one has denied the doctrine of the priesthood of all believers.

If you have never read Rob Rayburn's lecture on this subject from a few years back at Covenant Theological Seminary, it fits wonderfully with what I am saying here. It's called "The Centrality of the Christian Ministry" and you can download it as an mp3 file or listen to it online.
http://www.covenantseminary.edu/resource/Rayburn_CentralityOfChristianMinistry101696.mp3
http://www.covenantseminary.edu/resource/Rayburn_CentralityOfChristianMinistry101696.m3u

The ministry does not replace Jesus, but stands in for him in his absence (he's in heaven) and serves his Bride in his Name. It's one thing to say that the pastor stands between God and man as a priestly mediator like Jesus. It's something else entirely to know that the Bible says that our Mediator Jesus uses our pastors in a special way to communicate his gifts to us. The pastor is not a mediator between God and man, but Jesus does use the ordained pastorate to communicate his will and grace to his people.

And there's a reason for this. It's to help assure God's people that what happens in the worship service is indeed the Lord's work for them. The people should be left in no doubt that Jesus is speaking to them and feeding them in the assembly – the presence of a ordained, robed minister helps them know this is true.

Just a bit more on the objection to pastor-led liturgical worship based on the doctrine of the priesthood of all believers.

First, there's a great deal of confusion about what a "priest" was in the OT before Christ transformed the world. In too much Protestant literature one gets the impression that the priests of Israel were akin to Roman Catholic priests and that we can rejoice because Christ put an end to all that. Sadly, it is an all-to-common mistake to identify the rites and rituals of the Mosaic covenant with Roman Catholicism. (I should say also that this goes hand in hand with the notion that the problem with the Roman church has been that she never quite got out of the Old into the New Testament.) It's just not the case. But all of this is impossible to explain in any detail here.

Suffice it to say that Yahweh did not deliver to Moses on Mt. Sinai a proto-Roman Catholic liturgical ritual system, especially as some Protestants often characterize Rome's system. If one grants this, then certain things follow. For one thing, we might actually benefit from going back and carefully analyzing the OT liturgical system of sacrifices. As I have argued quite extensively in my book, the way that the NT uses the language of "sacrifice" and "offering" and even priestly vocabulary to describe the worship of the saints in Christ, assumes that we know something about Israelite sacrificial rituals and are able to make the necessary adjustments given the new situation in Christ when applying them to the Church's worship. In other words, it's a good thing to study the sacrificial rituals for insight on how to worship. The New Testament encourages us to do so.

Second, priests in the old order before Christ were "palace servants." They were brought near to God in order to serve in his temple/palace/house. The Lord's house was a place of meeting, the location chosen by him in which Israel would find restoration and fellowship. Leviticus begins with Yahweh calling from inside of his house, the tent of meeting, and giving directions through Moses to the Israelites about how they are to "draw near" (qrb) and meet with him at his house.

Since "drawing near" to God was a frightening prospect for people that continued to offend the Lord of the house, Yahweh gives the protocols necessary for people to "enter" his courts properly. The climax of this process was a fellowship meal eaten with the Lord in his house.

In case you didn't make the connection, this is not much different than what happens when you invite someone to your home for a meal. We are, after all, made in God's image. If someone who was out of sorts with you knocked on your door, you wouldn't immediately walk into the dining room and start eating with him or her. No, rather, you would expect the person to patch things up at the doorstep or at least inside the door at the threshold of your home. We don't normally eat friendly meals with people with which we are not reconciled. So if you invite your neighbor over for lunch, something like this might happen at the doorstep:

"Jeff, I'm sorry about screaming out the window at you the other day. That chain saw was driving me nuts. I should have come over and talked to you. You had no idea that I was home to rest that day and the noise kept me awake. Will you forgive me?"

You say, "Sure, neighbor, I accept your apology. Come on inside and sit down for a while. Honey, would you get something for Sam and I to drink while we talk. Thank you. Now, Sam, I'm sorry, too. I didn't realize you were sleeping. I would have been happy to wait. By the way, how are things going at work for you. . ."

Eventually, you eat and renew your friendship at the Table. Now you can do all this yourself because you're only dealing with one neighbor and a handful of friends and acquaintances. You are not a king or a president who cannot meet personally with everyone. And, of course, you are not Yahweh who is throned above the cherubim in the Most Holy Place. Yahweh, the great Lord over Israel and the world, assigns priests to help him with these household necessities.