Yeah as you go up, a lot of things change, Tanking goes from tank and spank and mass pulls to watching the limits and strains on healers and good use of cds by everyone. Take for instance a group with a rogue dh and a fire mage. The rogue and tank might want to know what pulls can be skipped, what the most optimal trash is and what to blind. The dps need to know how to avoid aoe and (if available) ways to ease strain on tainks. Earth elementals, stun totems, ghetto cc as a interupt. etc.
More things start becoming one shots in 15s that you would have shrugged off before. Taking 50% of your damage might not be a big deal, but taking 120% of it at once is.
On the flipside everyone starts to (or generally needs to) learn which mechanics to avoid. Some classes can take hits better like rogues with feints and cheat deaths and leeches and fury warriors. Some classes have funky aoes where say fury warriors do well on your normal average 1-5 mob pulls of 1-2 mobs but in the blue moon of 10-20 mob pulls great. IMO for public pugs though i don’t get why fury warriors are so bemoaned though, in 80% of pug situations where 3-6 mobs are pulled at a time, it hardly matters. Plus they can still do like 90-120k in plate with two charges and victory rushes and 25k self healing per second with the effective 60% plate armor of a vdh. (fun fact, Fury warriors and holy paladins have the same base armor as VDHs, ± 10%. 60.5% armor (fury/arms) 459 ilvl to 59.8% armor 470 ilvl Vengence ) So basically anything that hits a leather for 400k in the one shot range will take like until the 700k equivilent range. So plates on the other hand get dented but more time to heal. Leathers have ways to mitigrate and time defensives but dodge as a mechanic is fun with lots of small hits but casino roulette with 40 one shots. Problem is, on teaming, anything can have a one shot and with 5 mobs and interupt orders it can get chaotic.