FYI, this is mostly a Lightning main, Sasuke, and Hinata combo. The fourth character really matters very little.

That's why Karin and Kabuto are options, sure, but you c*so use Neji or Choji and get * amounts of combos. Neji has the advantage of being tankier than Hinata and can stand in front with her while silencing enemy jutsu while Choji has the advantage of spamming Knockdown with every move he makes which triggers your 8-hit combo all over again.

So you actually have a lot of choices which character to use as the filler. I personally have been using Choji for weeks with this team because he gives me a low cost targetable jutsu that murders the crap out of whoever I want while being a decently tanky guy himself. I'm probably going to switch to Neji but Choji is already 3-stars while Neji is still only 2. Plus Neji gets fewer combos, only 7 max with this team.

I would actually pick any of these teams over your "Sasuke stands in front" formation because Sasuke is literally the reason you get half those combo hits.