We killed Hydross tonight, really easily in fact after playing with a new strat. With the new strat we were using today this is probably the easiest boss in the game so far; most of the effort you need to put into him is really in farming up the tank gear, and learning to clear the trash efficiently. Well, and the whole attunement thing takes some time. To sum it up, Hydross seems appropriately placed in terms of difficulty and risk vs reward.
Magtheridon will probably be the guild's next big focus.