They work best when used in groups of 2 or 3 for lower level pvp. (Dread Muffs and Hero helms for 15, all gears for canta) This way they are providing (using 2x) +20 to at LEAST 3 useable stats, if not 4...
Casters would get 20 int/wis/luc/rec (and DEX if required for their build)
Others would get 20 str/dex/rec/luc (and WIS for resist if it gets fixed)
I wouldn't really see too much point in only linking one (except helms, that's actually a boon).
For instance in 1-15 caster muffs: Triple Mystic, 3x Star lapis.
That's +55 INT, +50 WIS, +30 REC +30LUC (and to a lesser extent, DEX) by linking only 4 lapis.
Prior to this players would link: Triple Mystic, Mystic 6, Wise 6, Mystic 5
Giving: 75 INT, 50 WIS, and NO REC/LUC/DEX. Therefore sacrificing 20 stats to gain 60, for a net gain of a useable 40 stats. (omitting DEX)
Therefore, only sacrificing 20 INT (30 damage) for a slight crit chance bonus (which is nice in 15 pvp) and some more defense/hp from rec.
Similarly can be said for Melee/Ranged physical classes. It affords them an opportunity to link STR/LUC into a place where it normally couldn't. Ie: Triple Craft, Triple Shrewd, 2x STAR for archer/hunter >>>> +45 STR, +40 REC, +45 DEX, +40 LUC, whereas otherwise provided would have: Triple Craft, Triple Shrewd, Shrewd 6, Shrewd 5(or safe 6) >>> +25 STR, +20 REC(or 50 REC), +75 DEX (or 55 DEX) , +20 LUC. Sacrificing between 20 and 30 stats to gain 30 stats distributed differently. (higher DPS, slight loss on survivability)
It seems to be stronger in casters, however, it does have its advantages.