I like it but a couple of things cross my mind here. One is every defence is pretty close to identical. Getting some more differentiation there may make the monster more interesting to fight for your PCs.My other concern is that the creatures defining feature seems to be a shift between being ranged artillery and this really bad ass melee combatant. When that slam attack works your players are sure going to notice which is great but I'm concerned that in most combats it may not really come up because the Grey Ape is being locked down by a high AC defender where its unlikely to get off two hits.
One way to get around that and show this off its pure brutality is possibly to give it an encounter power that kicks in only when first bloodied that allows it to ignore marks for one round. If the tactics mention that it should save its action point for this moment you'll hopefully get a chance to really drive home the switch from artillery to bloodthirsty melee combatant to your players by the simple expedient of having it do two of those double slam attacks on some low AC party member like the mage or rogue. If you pull off the onging damage as well, so much the better.
There are other ways to go about this as well, of course, but my main point is considering something that really highlights the switch over too your players.
Excellent ideas. You're right, giving the creature a power to avoid marks would allow the ape a lot more freedom to run rampant and prevent it from getting pinned down by the defender. Plus, as an elite it’s not really a big deal to add another power to it.
I should be able to update the Shadow in the Trees this weekend or Monday.I have to admit, I never really give defenders the attention they deserve when I'm designing combats (a blind spot of mine) - probably because my own interests as a player center on strikers and controllers.