no one on my server crafts the guardian hilt 27 yet (i don't think anyone is even bothering), i've noticed most tanks just using might 27 - is it for this reason? Better threat generation aside from taunt stacking?
Yes, it's pretty much for this reason. I don't even bother using the high End armorings or hilts on my tanks when given the option. You get all of the HP you need tangentially. Most of the Endurance on the high End armorings ends up being redundant, especially for Guardians and VGs who get no mitigation benefit out of higher hp, whereas higher strength equates to higher damage, higher threat and, in the case of Guardian tanks, some degree of improved mitigation (not that much because the conversion from Bonus Healing to Blade Barrier is friggin' terrible and still kinda questionable as I see it).