Most non-magic people are rocking 3-5 Piece Impenetrable, plus adding that with the Reduce Crit Damage CP, critical builds aren't very good anymore. Now that's not saying they don't pack a punch. My C-Frags crit for around 31K and in PvP that goes down to 14.5K. However, when I hit most stamina builds, disregarding spam rollers and shuffle proc, it crits for around 9-10k. That's low...like really low.
So a lot of top-end PvPers wear a lot of gear with Impenetrable, which increases crit resistance, and some folks run certain sets that give crit resistance to group members, and that sort of thing. Knowing this, you'd think crit builds would be crap. This has not been observed. The reason is that the vast majority of players, and even a few top-end players, have little or no impen gear. Thus, your odds of getting a juicy crit on an enemy are still very very high.
So just don't try to duel a pro or try to burst down anyone Legate or above and you should be fine.
Men'Do PC NA AD Khajiit
Grand High Illustrious Mid-Tier PvP/PvE Bussmunster
I've had plenty of success with a critical build. I've used shield breaker with precise dagger's. With this combo i can take on magicka build's with shield's with ease but also critically hit stamina build's more often.
Without Shield-breaker, you will be at a disadvantage against any build using shield's. Considering Harness Magicka will include Physical damage next patch, all magicka build's next patch will have 100% critical resistance with that shield active.
Sooner or later you will be able to critically hit shield's, it's just good for balance reasons (it will happen eventually), until this happen's critical build's are not as viable compared to just stacking weapon damage.
I'll always use Dagger's just because they look cool though.
Are Critical build's good for pvp? YES
Are they balanced atm (due to un-crit-able shield's)? No
Are they effective? If you avoid shield user's yes.
I go for Spell Damage/ Weapon Damage or Max Stats. Never personally go for Crit, as people often run lots of Impenetrable (including CP).
If your damage comes from raw power instead of crits then you will cause all of their Crit resist to be wasted CP/traits. That's how I think of it, and it has worked great for me so far!
On a side note, Stacking Crit+Crit Damage is the way to go for PvE DPS.