Guild Wars 2

A-Net just fixed Communal Defenses making it only target 5 allied players, yes it was broken on open world with unlimited targets. But now its just a bad trait as you need to take valor for it one of the worst guardian trait lines.
Same go for venomous aura for thief, now its base line which was a good thing, but it make Condi Thief worst, as the biggest reason for you to pick it was share Basilisk, now the Power Thief that is miles ahead of condi can take it if needed, 0 reason for a condi thief.
My suggestion is that a-net starting looking for these traits and just buff then changing 5 players to 10. For example give Leeching Venoms trait a buff that make yours venoms target 10 players instead of 5. Now you have a reason to take condi thief for raids or WvW. With venoms for 10 people you will want a condi thief comboing with reapers Epis.
Communal Defense to 10 targets would make people consider it for raids.
I’m sure that there are other traits/skills that if A-Net changed to 10 player instead of 5 would see play. So now we would have another way of balancing things, for example mesmer signet of inspiration, it is already strong it would still be only 5 people.

I don’t think making the trait do it is the right way to go about it.

Atleast when it comes to condi’s and boon’s respectively.

If they want to go this route they already have the stat system in which they can use both Expertise and Concentration respectively to boost allied targets effective use of condi’s and boons.