From what I understand, necro is typically considered more of a carry than singed is. I never actually played dota1, so I cant compare heros until theyve been put into dota2 >_>
And yeah, cleavers atm are pretty broken. Not sure why riot forgot to put unique passive no them :\
Well neither of them are typical "carries" from my understanding.
Anyway, Bristleback is actually a really hilarious hero. His design is in the same vein as Singed, but he does his job in a much more hilarious and interesting way.
See, Bristleback's name has a purpose. He's an Armadillo who can shoot out spikes in a large aoe around him every few seconds. These spikes don't do that much damage inidividually (say like 30 physical damage per hit), but they stack in intensity. The more times you've been hit by the bristles, the more damage you take, up to some ridiculous amount of damage.
So now it's obvious what he wants to do: Stay alive in a teamfight - the longer he stays alive and keeps spamming his spines, the more deadly he becomes. However, he has a really unique way of doing this, which is what defines the hero, and gives him his name. Any damage Rigwarl takes from behind is reduced by 40%. Any damage he takes from the sides is reduced by 20%. His ultimate gives him a lot of movespeed and attack damage, so this is what he does:
Runs into a battle, starts spamming quills. Starts auto-attacking an enemy hero. As soon as they go to focus him, he turns around and runs away, so that all the damage they do is hitting his back. IN ADDITION, once he takes enough damage to his back, he releases another set of free quills; so in actuality, focusing him hurts your team even more. Killing Bristleback is completely positionally-based. If you can catch him while he's facing your team, you can kill him relatively easily, and without much cost. However, if he can turn around before he gets stunned or disabled, or you can't attack him from his front, you're going to be bringing a LOT of pain upon yourself.
http://www.youtube.com/watch?v=P-1mQg1l60s&hd=1