Tryn, Nasus are.
Jax has a huge AoE stun.
Fiora isn't as bad ONLY with skill enough to proc ulti, but not way too far above the worst.
Trundle literally makes the enemy tank your team's squishy pickings, he's always powerful for a teamfight.
Riven as long as not tilted and crap, can actually chain CC for her team then execute/chunk with ulti recast.
Irelia's passive makes her a backline menance and huge agro magnet.
Pantheon does fall off heavily, but he does still pack a nice burst cc to grab a target for the team to focus.
Tryn gets less value when mutliple focus him but he does do a lot if his team can draw even the slightest more agro than he is.
But nasus just gets outright kited too heavily, not to mention true dmg, % max hp damage, and LW just make his immobility super dire. even at 1000 stacks if CC'd and killed or grevious wounded just as he Qs his effectiveness is just gutted. not to mention it's not like Q is true dmg, it will get mitigated.
Nasus is by far just a big no. Might have to name some other champs, cause I forget any other splitpushers. My personal splitpusher is shaco, but his teamfight is good ONLY if you set up boxes like a maokai/teemo and "ward" the area, it even sets up picks and retreat paths as long as you continue doing so even with mana restrictions.