Na!!! You better focus targeting the add on the MT and watch for friction! splipstream isn't the right spell to focus on!!!!!
I'm used to MT with chirada on me (and not suparna), so this may vary a lil bit when tanking suparna, but basically :
first sisters pop is simple :
Garuda+chirada both cast slipstream at the same time
chirada casts friction
Both cast WW at the same time (actually chirada's spell isn't WW, but it's the same damage output, so nobody cares :p)
double slipstream again
friction again
double WW again (but usually, OT already got back aggro here)
In tornado phase, it's a bit more tricky :
Garuda casts slipstream
chirada casts slipstream and at the same time Garuda invokes the tornadoes
Chirada casts friction, Garuda casts WW 1s after
one or two secs after, chirada does her WW (which is still not WW)
and so on
So basically, there is no more "double WW" in tornado phase, just "WW then another after 1/2s".
My advise is the following :
Focus target the add on the tank, and rely only on friction to predict incoming burst
Cast eye for an eye on the MT as soon as he is positionned in P1, or as soon as he throws his shield in tornados phase
Cast virus+stoneskin when friction starts
wait something like 1s
Start casting cure 2.
As I said, timing will change a lil bit if MT is tanking suparna instead of chirada, mainly because of the jump, but it's more or less the same
