Your PCs are (in my opinion) highly optimized. In your experience, does that put more stress on 6E's rules than it does to 5E's?
Yes and no.
In 5e, you could create an armored cyberlimb bearing, heavy milspec wearing, soak dice optimized minotaur juggernaut that could be packing soak pools in the 60 dice +11 automatic hits from the milspec range, plus just be immune to attacks that have a combined DV+AP of less than 23 literally out of character generation. Other than direct combat spells, no
reasonable opposition will hurt that character, not even the triple-tap sniper without an improbable amount of net hits.
In 5e, you can build a mystic adept with such a high defense pool that only another mystic adept or adept with an unreasonably high rating weapon foci, running both analyze device and benefiting from a technomancer's machine sprite diagnostics will have a snowball's chance in hell of ever hitting them.
The same is true of resisting magic. After you have your base (usually) two quickened increase attribute augmented attributes to resist the spell, then add your ranks of adept spell resistance, and counterspell skill, and body+magic+initiate grade from harmonious defense, not even the likes of lord gwyn, harlequin, and lowfyr with their magic attributes 30+ could land a spell.
5e was the system of supreme defense where you couldn't be touched by anything in the ballpark of an equally advanced opponent if you chose to build that way.
6e overall is more balanced towards the center at the "base level", but when you compare the optimized levels vs. one another the entire thing falls apart with offense standing victorious.
The attack pool vs. offense pool is it a good ratio. You basically have agility + augmentation, plus 1 from smartlink, plus 1 from reflex recorder, or plus improved ability and plus weapon foci rating vs. intuition, reaction, attribute augmentation (favors mages), plus combat sense (adept only). That default favors offense calculations, but when you factor in action options of block, dodge, and full defense it evens out well enough.
Damage vs. soak is the opposite of 5e. At the low end of offense, it is decently balanced. I would say average soak pool is probably 4 or 5, with the absolute max being 14. Against small arms like pistols, knives, and clubs around DV 3P, that scale holds up decently. When we get into FN-HAR burst firing explosive rounds for 8P, a troll punching you in the eye for 11P, or a grenade exploding in your face for 16P, it completely breaks down to the point of being insulting to suggest the person even bother to soak if they get hit.
Overall 5e is more broken, but broken favoring PC survival vs. broken favoring PCs being evaporated. Literally all it would have taken would have been me to give each of those five adepts a single grenade at the end of our play and it would have been a guaranteed party wipe.
I think playstyle is going to be an even bigger issue for 6e than 5e. Players who's style differs from their GMs are going to have a much harder time having fun.
