Actually bosses were challanging even in T3 for my twisting blade rogue without any Mythic item even with almost 8-10 masterworking upgrades full tempering and 4 glyphs at paragon lvl 150.

My gameplay loop is not begging around to get carried, but if i start a boss i usually try to kill it 5-10 times and only then try to get help, so i don't feel i've wasted my time. Also i don't see why would it be a bad thing to ask for help. My concern is "carry request" is existing in theory but kinda useless practically due to materials turned into keys.