Early game they are useless at defending due to extremely long cooldown.
Lategame missing a shot is most of the time giving yourself a tremendous disadvantage considering they cant shoot again, and can easily get focus fired
My propositions. Give the disruptor 3 different nova’s each having there own global cooldown.
1 short range, low cooldown, small aoe size, explodes fast. (10 sec cd)
2 medium range, medium cooldown, normal aoe size, explodes medium. (30 sec cd)
3 Long range, long cooldown, big aoe circle, explodes slow. (60 sec cd)
If you use 1. all the disruptor abilities should go on the same cooldown dependant on wich of the novae you use.
This change would give the disruptor more flexibility during the early stage when getting allinned, making sure you most of the time have access to the novea, but seeing the nova is small it wouldnt automatically stop any allin by getting off a ‘lucky’ shot, yet it would also be more forgiving to miss a shot due to low cooldown.
Midgame the current disruptor isnt too bad seeing it can severly weaken the enemy forces and force out favourable engagements, but protoss has other units besides the disruptor to be able to defend if the explosion misses.
lategame the current disruptor either has too long of a cooldown. Doesnt shoot fast enough. and has no true harrass potential due to small radius of the aoe.
Also hitting behind long range units is practically impossible with the current disruptor.
Giving it access to a long range high cooldown ability gives protoss the ability to stop siegelines without being forced to use mass chargelot. Yet because of the long time before the nova explodes gives the terran the option to unsiege and micro away from it.
It also deals with terrans spamming liberators with range to stay active with there army and punishes terrans who dont look at there army when sieged up.
Versus zerg this could stop early roach/ravager pushes, prevent lurkers from hardsieging (same as tanks) and give the protoss another option to harrass (killing queens for instance with the short cooldown ability)