t6 is a lot easier than t5.
The bosses are all easier. Illidan is easier than vashj or kael. Council can be cleave/aoe’d down together (excluding the mage) making it a joke.
The trash is generally easier, less crazy mechanics like t5 trash. Hyjal of course just has tons of trash but it’s not particularly hard. The parse-monkey healers who stack red gems may finally feel some pressure, but they can still just use their bought gold to chug dark runes.
The trash drops are better (less weird/useless items ie spyglass, shaman relic, 7th ring of tirisfalen) and drop in both raids. The patterns are better, with less specs completely left out.
also the new stats haste and Armor pen are kinda broken and make the game much easier, as well as epic gems dropping like candy.
on the mega-buffed p.servers many guilds that couldn’t clear t5 regularly would clear t6 with ease, this is with HP /dmg numbers that are massively buffed over blizz nums
so yes it may take a bit longer but it will be easier for most guilds. i predict all the 8/10 stuck guilds now can easily clear it, maybe without archimonde