I consider Caliban a bad warframe. He isn’t bad in isolation, he’s just worse than almost everyone else. He’s probably in the bottom ten in my opinion.

Going through his abilities:

1. His passive does not stack with Adaptation. It’s an ability which encourages EHP tanking, but it gets invalidated by the best EHP tanking mod. It applying to allies is really cool - especially because it’s affinity range - but it needs to stack to be worth using IMO.

2. His 1, Razor Gyre, is unambiguously awful. Even Caliban fans call this one a helminth slot. The chance for a slash proc is cool, but the way its damage scales makes it generally unviable as a tool for killing enemies at higher levels. It can work at lower levels, but at those levels other warframes can clear trash better. (And it locks you out of his 3 and 4, which are probably his best abilities. That’s the same problem Hildryn’s 4 has, and nobody uses that.)

3. Sentient Wrath lifting and applying damage vulnerability is cool, but any damage un-lifts enemies. It suffers from the problems of other CC abilities - if I want to do a full body animation to cast an ability, I might as well just kill the enemies. Also, for some incomprehensible reason, it has a target maximum. Meaning even if you wanted to build for range and duration, you also need strength if you want to capture a large group of enemies. The damage vulnerability is nice, but it’s a little redundant to being able to full-strip armor/shields, since that’s enough to kill everything in all content you’d bring Caliban to. If an enemy has no shields or armor, it usually just dies. And if you really need full strip and a damage vulnerability, you’ve probably reached a level where your passive and Lethal Progeny stop functioning at all, meaning you’re going to be too busy dying to get use out of Sentient Wrath.

4. Lethal Progeny is a great idea with mixed execution. I love the idea of summoning conculysts to recharge shields and draw enemy fire, but the lack of scaling and prioritization of attacking over shield regen kind of kills it. IMO conculysts should somehow try to match enemy level, and at least one conculyst should always be assigned to permanent shield-recharging duty. Overall it’s still a fun ability, but its use as a form of enemy distraction is held back by the fact that it has a duration. If Wukong can have an infinite clone, I think Caliban can keep his sentient pals until they’re killed.

5. Fusion Strike is pretty good. The AOE full permanent armor strip is awesome, but the ability is a little long to cast, it’s in a cone, and this is Caliban’s main thing. Other warframes can armor strip better (like Hildryn, who can strip entire tiles in the blink of an eye with minimal interruption to your movement/gunplay.) It’s a powerful ability, but it’s not enough to carry his kit. It doesn’t help that Tharros Strike is a helminth ability, which is also a cone-based armor strip that requires 200% power strength.

Overall he’s just not great. He focuses on doing a lot of things badly instead of doing one thing very well. In a world where there are frames that can do lots of things very well, I just don’t consider him worth using. There’s never once been a single time where I’ve felt the need to use Caliban for something.

That being said, there’s nothing wrong with using Caliban if you just think he’s fun. Much like Atlas, he can perform well enough that you’re not throwing by using him or anything. I just think he deserves massive buffs, because there’s a great frame hiding in there that needs some work before it can really spread its wings.