Painwheel is fun and those three characters can work together, but you won't have any meterless reversals so you'll have to be very clean with your spacing and rushdown. It might be hard to stick with Painwheel if you're only using her because you don't think enough other people do so, especially because the beta patch might make her more popular anyway, but she's the closest character to Valentine and Robo in terms of playstyle imo so there's a good chance you'll like her regardless. Painwheel and Valentine love H beam assist, Robo loves H bypass assist, and for a Painwheel assist you could pick L pinion to control a lot of space with very fast startup. Valentine might like Painwheel c.MP or s.MK assist for lockdown, but Robo wouldn't get as much from it. So if you want to play those three characters you could probably make it work. Valentine/Painwheel/Robo would give you maximum rushdown with beam assist and decent reversal supers on your second character to help you escape bad incoming situations, Valentine/Robo/Painwheel or Painwheel/Robo/Valentine would give you better Robo zoning and let you build meter with your point character and DHC into level 3 beam for huge damage, and Robo/Valentine/Painwheel would give you very strong Robo zoning at round start with the option of DHCing into scalpels to rotate your team into the first order I mentioned. If you end up not liking Painwheel I think you'd be most likely to enjoy Double (L or M hornet bomber), Parasoul (napalm pillar or L or H napalm shot) or Ms Fortune (H fiber uppercut). They all have reversal assists too, which helps your team. There's always Beowulf (H chair) and Big Band (L beat extend or H brass) and Filia (H updo) too, which would all work well with your team but have very different playstyles to your other characters so you might not like them as much.