What I would like from Tri-Disaster as someone who has played summoner.
Make it instant oGCD. Have it Stun the monster for 1-3 Seconds, Bind the Monster for ~12-20 Seconds, Have it increase the duration of all Dots placed on the Monster by 15seconds. Give it a 2-3M Cool Down.
Get rid of Garuda's Contagion skill and give it something else. Maybe a strong single target skill or a DoT of its own.
What I would like as a BLM to happen with Freeze and Bliz 2.
Freeze places a debuff on the monster that increase damage done by all fire spells. Make Bliz 2 require no MP while in Umbral Ice.
This means a new AoE Rotation can be (Low MP) Flare > Transpose > Bliz 2 Until first Tic > Freeze > Fire 3 > Fire 2 Until Less than 1100 MP > Flare > Transpose.
As a Monk
One ilm punch needs to be useful in some form. I have no idea how they could make this skill better, I honestly wish they would just remove it and replace it with a oGCD skill that refreshes your GL or gives you one stack of GL with a ~2Min cooldown.