Ships with ECM Jammer bonus are overpowered in many scenarios. I can say this, because I have PVP experience vs ECM jammers like Griffin Navy Issue and other similar kinds with my FW ALT. If they’ll get on optimal, they can destroy slowly but truly every ship (even counter vessels like destroyers to Frigates) without enough tank, otherwise it will do anybody else which will arrive 20 mins later. Look at that Griffin, that little shitty antenna has 20% bonus to Small Hybrid Turret, which is more than Merlin has and can easily push 250 dps! Look at those videos or streams where a BS pilot fights versus entire fleet. Obviously he’ll blow up soon, for sure, and suddenly somebody brings a jam-jar, really? Is this a fear to lose something in return even?
Finally, I’d say the ECM issues aren’t based on its original mechanic, - ECM issues are based on how players are using this mechanic.
How it will be fixed finally? The main question is. I’ll suggest to look at WoW CC mechanic, which, I’m sure, is the best in MMOs with complex PVP mechanic.
https://wow.gamepedia.com/Crowd_control
And diminishing returns
https://wow.gamepedia.com/Diminishing_returns
For example, first Stun ability has 5 sec duration, the second one has a time duration reduced by 50%, the third one - has time a duration reduced by 75% and afterwards your character is immune for 18 sec. Diminishing return has a reset timer of 10 sec, if I remember it correctly. Therefore, a skillful player opponent will never Stun your character third time, because it will be a useless use of the ability (with cooldown) and will make your character immune to any available Stuns for 18 sec. He rather will wait 10 sec to Stun your character for full 5 sec afterwards.
Spell Silence works another way. It has diminishing returns based on schools of magic also. If a Mage is silenced during casting a Frost Bolt, then all his Frost spells will be Locked for 3s, 4s or 6s only (depends by counter). Anyway, this will let Mage to cast spells from other schools of magic like Fire, Arcane. The most interesting moment here is, for example, if Frost spells for a Mage are offensive by doing damage, then most Arcane spells are defensive like Polymorph (CC) or Blink (teleport away, MJD in EVE). So, being locked with offensive abilities it allows you to play defensively for a while, because during this time your opponent will try all his cooldowns for top burst dps, knowing that damage will not come back.