sindragosa is so damn hard!

ive participated in multiple raids with multiple different players and this is by far the hardest boss especially in phase 3. phase 1 and 2 is no problem But at phase 3 for some reasons the healing always fails due to the debuff

from what i understand , those targetted with ice tomb must either stand at the head or tail of the boss away from the raid in order to form a block where raid group can reset their debuff by hiding behind the tomb . After that dont destroy the ice tomb , just leave it and use it for LOS to reset debuff, am i right?

Also someone tipped me off by telling me mages can just cast indefinitely and stack debuff and then just iceblock to escape taking damage from debuff.

can someone confirm with me this works and how many debuff can i afford to stack? can i stack up to say.... 99 ?

Should i change my dps rotation and go for spells that deal more damage but has a longer cast time? like pyroblast instead of fireball?

Is it advisable to put on frost resist gears?

First tomb goes to the head side(tanks in range of healers). Everyone keeps dpsing till they get 4-5 stacks mystic buffet, then everyone go reset stacks behind tomb. Start to dps tomb, meanwhile second tomb is up, which goes to melee spot - at the same time Blistering is cast. No one get pulled by it because they are behind tomb. First tomb is killed, second tomb is killed and everyone goes back on boss. Repeat.

Now, how it actually works, since everyone is overgeared. Nuke boss and tomb goes to other side of the boss. Ignore tomb. Maximum you will have 2 unchaineds. Everyone saves their ice block, bubble and whatever, keeps dpsing with unchained and before it goes off removes it. Simply ignore second unchained because boss will die before it expires.

So as a mage you get unchianed, cast for 30 secs, iceblock, and cast till boss dies. Sometimes you might get into situation where you cant remove stacks. Then you simply /dance for 30 secs, or if your group is absolute potatoes you go away from everyone, cast few stacks, let it blow, repeat. That is in Heroic. Normal mode - just dps, to die you have to put an effort for it to happen idk.