You're right, I had this trouble when I tried to play Gangrel. Animal Succulence does nothing, and attacking him just gets you sent back for not being stealthy enough, even though you're supposed to kill him.
Try this: Advance while crouching, but no further than the edge of the crates. Just try to get his attention, and get him to come check things out. When he starts coming, back around the corner and activate Animal Succulence, and anything else like Protean. When he reaches the edge of the crate, come out of hiding and attack. It only makes you start over if he spots you while he's out in the middle of the room.
This is how I got past him the first time with a Gangrel, and I just tried it again to check it out. Animal Succulence plus another discipline, and don't reveal yourself until he's right next to the crates.
PS- my Sneaking feat was only a 2. My guess is that if it were higher, I'd have a hard time getting his attention without going out into the room, which gets you sent back.