We use the alternating 2 stack points for the ranged method right up until we get empowered whirling corruptions., it phase 1 is going fine for you stick with that strategy until phase 2. we'll generally have 1 ranged assigned to nuking each weapon, and calling out for help if they aren't going to get a weapon down before the next intermission. We keep melee on the boss and just heal though the non empowered whirling corruptions, rotating raid CDs for each one, once they're empowered the melee run out, still popping CDs and rotation raid CDs, and the ranged spread round the room, each trying to take and add and kill it on its own. you've got 3x Devo Aura, 2x Rallying Cry, and 2x Demo banner that should be enugh to cover every single onewhirling corruptions should not be an issue, especailly ig peeps try to roatate personal CDs.
Looking through your Death Logs, the add tanking in Phase 1 looks chaotic as hell, it would seem that Blacklore really shouldn't be taking the boss and all the adds, So Terroraz really needs to work on keeping the adds off the melee, luckily he's a warrior so can be dropping a mocking banner once the first round of adds get near the middle, that should give him the initial vengeance to just keep rolling the adds, if Blacklore works with him and just tunnels the boss.
in the transition phases the tanks need to tank the adds, which means they, and the melee can't move to the next pack until the current pack is dead in the jade temple. ALso all the deaths to annihilate are just bad. if ranged/healers can't move out of it tell them to be closer to the boss. if you've got your face in Garrosh's Crotch, a couple of stops left/right/through are all it takes to be safe, if you're 30-40yards away you just aren't going to relaible get out of the cone without spending the majority of the time moving and unless you're a hunter that's a straight up HPS/DPS loss
MCs shouldn't be an issue if everyone but the person tanking Garrosh switches to them, interupts are priotiy blowing them up afterwards. Stuns, Silences, Dazes, knockbacks, all manner of thing work until they're empowered only interupts will work after that. on our alt runs i tend to DG MCs in the ranged stack point to the melee as this will break the cast and mean all the melee and both tanks can get on the MCed person.