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I think that archers should be evaluated not by their level and strength, but by their accuracy. And in this case, the Great (Royal) Elves definitely rule, as they are accurate and shoot twice.
Medusas generally shoot just to annoy. Shooting 4 times is simply to irritate the enemies.
Titans should not be considered at all, as they are out of competition (the only shooting unit of level 7).
And here is my rating:
1. Royal Elves
2. Archmages
3. Archers
Of course, there are many caveats here. For example, Thunder Elementals are better than Archers, but I personally don't like the Conflux (no offense).