I’d actually put him around about an “Equinox if she was a functional character”. Similar problems that make him unappealing unless you already like the frame or the concept too: he mashes together a whole lot of absolutely everything, but diminished with a “hybrid tax”. Other frames can do one or two things that Caliban does, and do it more effectively, but only Caliban does all of those things at once. I’d say it doesn’t help that he’s neglected and has a pretty bad bug too; currently Sentient Wrath is not applying properly through Overguard.

As an active Caliban player and having labbed him extensively recently, I’d say he has a lot more going for him:

The mini-Adaptation is only 1/5th as effective as the real thing, but it’s free and opens up a mod slot. It’s also twice as good as no Adaptation at all while you ease into the Arbitration farm!

With Arcane Aegis (and potentially Barrier on top), the mini-Adaptation shines with the Lethal Progeny to make him exceedingly durable. I tried a build with no defensive modding outside of Aegis/Barrier and pushed into the mid 200s on SP Conjunction Survival, which is more than my health conversion builds can do.

He has a good crowd control and personal defense kit with every single ability providing some kind of CC, including a moderate taunt from his Progeny.

Fusion Strike isn’t just full defense removal, it’s a large and persistent hazard that can be placed three times, so you can place it over potentially multiple choke points and fullstrip enemies as they come to you or an objective.

He definitely needs some augments and a bugfix pass though.

(I should say I love Equinox too, and mainly play Nightquinox, but DE has mistreated that poor frame so badly and half her kit is just inadequate nowadays.)