Sorry for the lengthy cut and paste, but I think this quote from Melancthon’s Apology of the Augsburg Confession answers pretty much sums up the key points. I’ve highlighted some relevant points:
"4]
Our Confession approves honors to the saints.
For here a threefold honor is to be approved. The first is thanksgiving. For we ought to give thanks to God because He has shown examples of mercy; because He has shown that He wishes to save men; because He has given teachers or other gifts to the Church. And these gifts, as they are the greatest, should be amplified, and the saints themselves should be praised, who have faithfully used these gifts, just as Christ praises faithful businessmen, 5] Matt. 25, 21. 23.*** The second service is the strengthening of our faith***; when we see the denial forgiven Peter, we also are encouraged to believe the more that grace6]truly superabounds over sin, Rom. 5, 20.
The third honor is the imitation, first, of faith, then of the other virtues, which every one should imitate according to his calling. 7] These true honors the adversaries do not require. They dispute only concerning invocation, which, even though it would have no danger, nevertheless is not necessary.
8] ***Besides, we also grant that the angels pray for us. ***For there is a testimony in Zech. 1, 12, where an angel prays: O Lord of hosts, how long wilt Thou not have mercy on 9]Jerusalem?
Although concerning the saints we concede that, just as, when alive, they pray for the Church universal in general, so in heaven they pray for the Church in general, albeit no testimony concerning the praying of the dead is extant in the Scriptures, except the dream taken from the Second Book of Maccabees, 15, 14.
Moreover, even supposing that the saints pray for the Church ever so much, 10] yet it does not follow that they are to be invoked; although our Confession affirms only this, that Scripture does not teach the invocation of the saints, or that we are to ask the saints for aid. But since neither a command, nor a promise, nor an example can be produced from the Scriptures concerning the invocation of saints, it follows that conscience can have nothing concerning this invocation that is certain. And since prayer ought to be made from faith, how do we know that God approves this invocation? Whence do we know without the testimony of Scripture that the saints perceive the prayers of each one? 11] Some plainly ascribe divinity to the saints, namely, that they discern the silent thoughts of the minds in us. They dispute concerning morning and evening knowledge, perhaps because they doubt whether they hear us in the morning or the evening. They invent these things, not in order to treat the saints with honor, but to defend lucrative services. 12] Nothing can be produced by the adversaries against this reasoning, that, since invocation does not have a testimony from God’s Word, it cannot be affirmed that the saints understand our invocation, or, even if they understand it, that God approves it. Therefore 13] the adversaries ought not to force us to an uncertain matter, because a prayer without faith is not prayer. For when they cite the example of the Church, it is evident that this is a new custom in the Church; for although the old prayers make mention of the saints, yet they do not invoke the saints. Although also this new invocation in the Church is dissimilar to the invocation of individuals.
14] Again, the adversaries not only require invocation in the worship of the saints, but also apply the merits of the saints to others, and make of the saints not only intercessors, but also propitiators. This is in no way to be endured. For here the honor belonging only to Christ is altogether transferred to the saints. For they make them mediators and propitiators, and although they make a distinction between mediators of intercession and mediators [the Mediator] of redemption, yet they plainly make of the saints mediators of redemption. 15] But even that they are mediators of intercession they declare without the testimony of Scripture, which, be it said ever so reverently, nevertheless obscures Christ’s office, and transfers the confidence of mercy due Christ to the saints. For men imagine that Christ is more severe and the saints more easily appeased, and they trust rather to the mercy of the saints than to the mercy of Christ, and fleeing from Christ [as from a tyrant], they seek the saints. Thus they actually make of them mediators of redemption."
bookofconcord.org/defense_20_saints.php
(I forget which Lutherans these are…)