The best assist for beo is hp. Hurting hurl. It's an invincible dp assist that you can convert off of, and it's also an overhead in the corner, hits full screen, and keeps people from jumping or forces then to block if they were in the air. It's crazy good.
Lp. Hurl is a disjointed low that you can also convert off of, also really good but depends on your team and what you need, most characters already have good block string high low mixups.
The gimmick assists are cr. Hp and hk, where you start beo point, do a combo that gets rid of chair, tag out set up then you have giant af armored arm launcher or full screen sweep. Also really good but not hp.hurting hurl good.
For robo her best assists are hp beam (lock down, combo extender, great neutral tool, although it can be push blocked and crouched under), st. Hp (lock down, 1 hit of armor, extender, etc. Better than all the danger kick spins by principle iirc) and the mine assist (takes 2 calls to be useful, but you can call mid combo and then end it wty a 2nd call. The mine doesn't go away unless robo gets hit so it stops combos, controls ground space, and allows conversions)