Not really worthwhile if you're only looking at that set bonus. Too low of a chance.

Lightning Cage is definitely better, and Stoneskin is better as well.

Stoneskin definitely better, but a 6pc protection with lightning cage is still worthwhile once you are accumulating tons from hydra.  But definitely not a set (unlike stoneskin) which you can force with mediocre stats.

I'll do some experimenting, probably with Krisk, since he's in a team with Candy (whom I recently switched to Lightning Cage) and also in my Hydra team. 

i use protection gear, usually on the same champs as those who run stoneskin, its good gear and you can get 6 star mythics with nice rolls if lucky.

Can you elaborate on stats for protection and stoneskin

as a specific concept:

Stone Skin's effect is so very strong (at 4 or 6 piece) that we're willing to give up overall stats to get there.Just because it's so meta defining right now in Arena.

Protection is a much more niche set that hasn't seen as much play and - for now - lacks the same use, nowhere near the level of Stone Skin. Thus, we are often going to need better overall stats to make any Protection builds viable. 

I'd like to see any protection builds/teams you end up going with and hear how it goes. (or anyone reading this thread that's using it now)

One person specifically that I could see Protection being valuable for would be Nekhret, since it'd protect the buffs he automatically places at start of combat.

Is Stone Skin effective in areas other than Arena?  I have only used 2 pcs to get some basic stats.  

Not the best gear, but it helps in Arena. Of course a lot of RNG is involved. I'll need a RES banner to make sure he can resist Head of Mischief (he moonlights as a Hydra champ, too)

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I think his Ally Protect is already protected, right? But yeah, that's what I was thinking, Krisk's shield is a big part of protecting Candy in my team.