Stuff that needs fixing
1. The smaller missile trails are really 'patchy', as Maelstrom pointed out. I noticed the missile trail for that big missile looks fine, however, so you might want to change all the missile trails to follow that one.
Patchy trails might still look acceptable if they're more 'connected' with each other, but look more random in shape, and they should dissipate slower.
2. The muzzle flares last too long. From the video, the most obvious example of this are the Guardian's muzzle flare FX, it lingers for one whole second before very obviously 'changing' into smoke.
Muzzle flares should, by right last only a few nanoseconds before disappearing, unless its a rapid fire weapon such as machine guns, miniguns or chain guns which seem to have an extended-duration muzzleflare, but its really due to the rapid-firing of multiple bullets.
3. Missiles and other projectiles like the Bertha's plasma shots should travel
alot faster. Now it just looks like they're out for a Sunday flight.
Take a look at
World In Conflict's muzzle flares, missiles and explosion FX, it has some of the very best i've seen in an RTS. You should also take note of the projectile speeds in the game.