would it be a viable strat having all but 2 players stacked in melee and the other 2 in ranged area, having only those 2 controlling where the tornadoes land
Not really because you would then either have to spread before he does wind step or all players will get the debuff, which can one shot you combined getting hit by unseen strike just as a tick of the debuff hits you.
Tornadoes aren't that bad, our raid group starts the fight on the left side of the room and move to the right after 2 unseen strikes, then move to the middle after another 2.
Tornadoes aren't a problem if you do this.
You'll get tornadoes on melee this way. Tornadoes target ranged and heals, not dps or tanks. You'll also get windstep debuffs on many players, and this is not fun to heal.
My guild does the same strat of moving. Around 60%, after the next unseen strike, we move from the right side to the left side. That way we start fresh with no tornadoes for the 2nd half of that phase, ~60-20%. Makes them not a big problem.
We've tried having ranged DPS and healers stacking in melee even with 10+ people still standing out.
We've determined by the fact that he still targeted the few ranged and healers standing in melee that he targets his tornadoes based on spec rather than distance, and seems to allow monk healers to be in melee.
Split the main room into 4 sectors - the boss platform, the entrance to the right hallway, the room entry and the entrance to the left hallway. First spread loosely arround the boss platform. Classes that can move very fast (mage -> blink e.g.) can stand far away, the others a little bit closer. Try to keep the tornados in this area and avoid tornados in the middle of the room. Somtimes there will land one anyway because of unseen strike + tornado. That's not a too big problem, but you want to have space left in the middle to keep the boss there. After two unseen strikes you go for the right entrance. If it gets crowded there you go for the room entry. There you should actually have a lot of space left.
The way we did it on normal and heroic was to drag the boss to the stairs (where he starts) and have all ranged/healers stand further up the stairs, to the sides. If we get overcrowded we move to the entrance and do the same on the opposite side, meaning we never have any tornadoes in the gauntlet area or where we stack for unseen strike.