I love the chroma armor and especially the deadly virulisk but does it worth this armor to spend my cr there? is it useful?
chroma suit
In SK, you should get a piercing defense set, an elemental defense set, and a shadow defense set each with normal defense in my opinion. Seems like it is sort of how the game works.
If you really like how deadly virulisk looks, then get it. The extra bonuses from skolver or justifier make those sets better as a piercing defense set, but you should not feel forced to get them because of that.
This game isn't too challenging... even when it comes down to it, the shadow lair that you want piercing defense for happens to be ice queen which is a ton of jellies. That makes deadly virulisk better than skolver there, assuming you prefer a damage bonus which not only applies to swords, but guns (or bombs) as well instead of having freeze def. You won't have a damage bonus for those lumbers but whatever.
But yeah, this game isn't really the most challenging game out there... you should go deadly virulisk for your piercing defense set if you like how it looks.
All of the chroma gear is highly specialized since the bonus is only against one monster family, but if you're going to be doing a lot of jelly farming they can be extremely useful. The bonus vs. slimes applies to ALL your weapons--not just swords, as with the bonus you get from vog/skolver. If you mostly use swords, I think I would stick with wolver, but if you like to mix it up with guns and bombs, consider picking up a piece of chroma.
Useful? Yes. As useful as shadowsun/nameless/skolver/vog? No.
With those sets, you can get asi/damage for one type of weapon. And the damage bonus applies to all monsters, so much more useful than a damage bonus just against a family.