With one tamriel many people including myself have tried a lot of different sets that dropped in the dungeons but some of them are definitely lacking improvements.
Take Sunderflame for example it’s 2 to 4 set is pretty solid (Max stam, weapon damage, weapon crit) but it’s fifth piece isn’t even good if you compare it to spriggan (5th piece Full Heavy attacks provides 784 bonus flame damage and reduce the enemys resistance by 3.3k for 8 seconds). In my opinion the flame damage dealt should be increased or the physical resistance taken off should rival spriggan if not surpass it.
Essence Thief is also another set that has solid 2 to 4 pieces but it’s 5th piece is considerably unreliable (Doing light attacks gives you a 15% chance to draw essence from the enemy. Collecting the essence heals you for 4150 health and restores 4150 stamina + increases your damage done by 12%). In my opinion it should proc off of both light and heavy attacks and the essence should be given to you immediately but there should be a cool down of 5 seconds in place or none at all.
Brands of Imperium is a ok tanking set but I feel it isn’t really what most tanks including myself would want. It’s got a pretty solid 2 to 4 piece (Max Health, Max Health and healing taken) but the 5th piece is another bad one. 11.6k damage shield is ok but not good, I think it’d be cool if the set provides a heal based on the damage it receives like lets say 5% or 10% of the damage received you release a heal to your allies. I feel that would be pretty good at giving the healer some breathing room.
Redistributor set (crafted) has a pretty balanced 2 to 4 piece (Max Health, Max Stamina, and Max Magicka) but the 5th piece is something that isn’t needed and I have never seen anyone use this set. I feel there should be no cool down for this set and it should proc if you’re healing an ally too (although that’ll be OP so maybe just getting rid of the cooldown is good enough). The set gives 2.3k health to an ally if you fully heal yourself while at full health.
There’s many more sets I could go on with like the undaunted weaver sets or other undaunted sets but in my opinion they all lack a cutting edge that would make it something you’ll be willing to grind in order to obtain.