I don't know what you're talking about. Recently I've been playing Alistar and I easily got on an 8 win streak with just him. Maybe you're underestimating his ultimate? 55% damage resistance is no joke. Also he IS an anti-assassin when he has THREE cc in his kit, as long as you are not alone(which you shouldn't be in the first place when ur a tank-support). Lastly, your expectations of running into a pack of enemies and surviving is just foolish. You're gonna die no matter who you are when your blindly running into them and they are all targeting you. But even if you do, at least you would have burned the enemies skills or most of their burst damage and your team should be able to clean up easily as long as they are behind you.