Nah, I don't think the gore and violence in Animorphs was too much. If anything, it was not enough.
For one thing, I did that "kill-counting" project for a while (to tally up how many kills each Animorph committed), and one thing I learned from that is that K.A. seems to like to weasel her way out of explicitly saying that someone died. So many times, it's really ambiguous whether someone actually got killed or not, and it makes it really frustrating to try to count kills. Anyway, I'm just bringing it up because I think the series would have been darker if they'd paid some more attention to each kill, and I think that would have made it better.
But, yanno, considering it was war and all, yeah, there's gonna be violence and gore. And I think the books even left a lot of detail out. A noteworthy example is in #3, when Tobias says something to the effect of "I won't say what happened next. That will be my own personal nightmare." Of course, that does have the effect of making the reader's imagination come up with what happened, which may almost be worse.