Reducing AoE damage through renown

[kaloel]

Intro:
Back in the days the target cap was 9, for every ability. On RoR some time ago it was raised to 24, for all skills hitting 9 targets. After some testing several skills had this change revoked and were set back to 9 max targets, because a 24 man KD or morale drain were too strong. Damaging morales were also nerfed and now have diminishing returns, to reduce morale bombing. In the end only (some/most) skills were buffed to hit 24 targets, without downside.
For some time now AoE is king. In every warband, every fort and every city both sides go for only AoE classes, if they can. Destro taking mostly choppas, sometimes marauders or melee squigs and, 1 or 2 magus/sorc and order seems to do the same. Everyone is specing AoE, even witch elves and witch hunters.
The intention behind this change was to reduce zerging, afair. Allowing smaller organized groups to hit and kill larger zergs. While this made it easier, for the underdog in <24 man scale fights, it made larger >120 man fights like keeps or forts incredibly stale. In the past weeks the only way either side has found is to wait for defensive moral 4s and push with those to mitigate the ability damage, and outheal the (reduced) moral damage. Then push in and pray you kill enough enemies with your AoE that the defenders can't res fast enough, until that 10-20s window is over, and you wait for another 5 minutes for the next m4 push. This is aggravated by the fact that the doors are choke points and the defenders can focus their (ranged) AoE abilities on this point to kill everyone pushing through, while the attackers can barely see any defenders near that choke point.

Problem:
Larger fights come down to who has more AoE, without any counterplay (or easy balancing). Making single target dps mostly obsolete and larger fights a spam fest without counterplay.

Suggestion:
Add a renown ability that reduces AoE damage for a limited amount of time. Spending more points could reduce the CD and/or increase the duration.

Reasoning:
This additional ability would allow dps' and tanks to get through the choke point more reliably, allowing them to enter the main room and fight there (and be killed by single target dps).
Adding this as a separate ability allows for an additional lever to balance AoE. If it is too good the cost, % reduction, duration and CD can be changed. If AoE gets changed at some point and is no longer a problem/ not a problem in a specific setting this ability will just not be used.
There is counterplay to this, by simply using single target abilities for the short duration it is active. While this is mostly possible in "smaller" <24 man fights it allows single target dps to shine even in larger scale fights, as they will still deal full damage to their targets.
This is mostly a band-aid fix. It should (hopefully) be rather easy to implement. (Any player ability that hits more than 1 target is AoE. There is an icon, and ability for it, "Resolute Defense", and the effect is basically a detaunt)

Worst case:
It becomes mandatory for everyone just like RD/CW was in the past.
If it is too strong it can be changed/ nerfed, as mentioned above.
If it is too strong in anything small scale (6v6 or 12v12) AoE is definitely too strong. In this case AoE damage should be quickly nerfed, as small scale is where single target damage should shine.

TL;DR: Add a renown ability to reduce AoE damage taken.
10: Reduce incoming AoE damage by 50% for 10s, 5 min CD
15: Reduce incoming AoE damage by 50% for 10s, 2 min CD
15: Reduce incoming AoE damage by 50% for 15s, 2 min CD