Ill go over things from a purely Pve Pov first then explain why this transitions to the major pvp problem.
Pve Goal - Chaos bolt is supposed to feel special to cast, it is meant to be like a nuclear bomb (It is meant to be spec defining)
This currently doesnt work because we exceed our intended ember generation by a HUGE margin
Blizzard have to buff Destruction somewhere for 5.4 because it is so not competitive its beyond silly with the Rof nerf.
Here is the issue,There is 'Nothing' you can buff while keeping there current design intent while keeping the current toolkit because of the following.
If you buff Chaos bolt / Incin / Conflag you also buff sacrifice and it will end up being stronger than supremacy.
If you buff immolate ember regen / damage then multi targets becomes a problem.
If you buff ember regen then we keep our current ember regen and the spec is played 'wrong' in blizzards eyes.
There is 1 buff i can think of that works from a pve pov and thats buffing the meta gem to be closer to 50% uptime or making backdraft increase damage of incin / chaos bolt instant at 3 stacks.
All of the above are purely from a pve pov, if i flip the table and look at pvp for a second.
If you buff damage of any spell people are gna cry a river.
If you buff the damage / ember regen of immolate it gets dispelled.
Backdraft giving increased damage could work in this enviroment, but instant Chaos bolt doesnt work (Think Chaos > shadowburn combos)
The biggest issue with the spec is that what blizzard intend for it to be in pve is the exact opposite of what is needed to work in mop pvp and this isint actually because of destruction being bad by design its because hard casting is so brutally impossible in mop
Edit - 1 Thing also, if Chaos bolt becomes instant cast then yes we are far to close to fire mages imo.