I have an idea.
Give only a single item in the set actual stats, but make it amazing (compared to SU/SSU), also preferred if it will be NOT class-specific. Like Witchhunter's hood, Neutraldin belt, etc - preferably only to armor pieces. Make all other parts including the weapon, blank (%ED for weapons or armor can stay because it's tied to base stats - or replace with a flat defense / damage bonus - or ignore it, not all builds need armor / weapon damage that hard). Also remove partial synergy bonus. Instead, add everything to the complete set, and make it both straightforward and good. There will be a part of similar stats between sets (i.e. +all skills, resists, etc, to give good baseline values, but not cap it to leave room for socketables / growth), and also a part of unique damage buffs (poison for poison, physical for physical), plus some orange text interactions.
It's also mandatory to rework the way one gets the sets, and I propose Nihlathak. He drops a catalyst item that you cube with five On runes (to make it sort of hard, but also rather easy and obtainable, and something you can work towards) and a perfect gem of desired color to get a full set. Gem color is responsible for the set you get, and there are 5 gem colors and 7 catalysts, one for each class, dropped randomly.
Sets should be balanced around level 120-125, plus orange stats. No MOs allowed, sets have locked stats.
Pros:
- Achievable endgame milestone guarantees a full set.
- Sets make sense now (you either go all in, or don't)
- you do not need to balance 175 (7 classes to 5 pieces to 5 builds) or whatever many there are, set items, as you only have 35 items with stats (one for each set), then a single set of baseline defensive stats, same for all sets, and 35 damage + orange unique bonuses, totalling 71 statset to balance instead of 175.
- Extension of previous point, removes useless items with useless stats.
- Sets provide stable, but suboptimal way of playing a build, so gives an incentive for casual players to get to (hell Nih) to get a good uberable gear.
- Farmable - you are not guaranteed to get a set you want from the first try, or even from fifth to be honest.
- if you get a set you did not want, you might be incentivised to try a new build, as you get most of the equip you would need. Fill the rest with TUs, RWs, etc, and go!
Cons:
- No sig material
- No stat variance
- Might be abusable to get guaranteed SU / SSU analogous equipment (not really a point, some TUs overshadow SUs in terms of performance (TU heavy belt, TU Greaves, TU Light Gauntlets, TU Setzschild, etc)
- More balancing and overall work for devs
- "Sets are good, just don't use them if you don't want to"
Of course I might have missed something, possibly obvious. Let me know if so.