The mods could be useful for destroying interceptor patrols at titans or Orthrus hunting, but not really worth it for Titan-bombers.
Agree, the -20% penality, guardian weapon limit, need to keep cold build and small oppotunity window to damage the Titan Core made it not so attactive, lets compare a 2A Guardian Shard with "potential" 135.4 DPS but with small clip (5 ammo) and 5 seconds reload, it have a sustained DPS of 54.89 - 20% =
43.91, 2E Sirius pre-eng AXMR (HC/RF) sustained DPS is
45.74 (counting 16 ammo clip and 2,27 reload time), so almost the same.
If AGZR mod could be apply on pre-end Guardian weapons, like ModShard (HC/RF) of course the math would change.
more comparison and math can be done for ship with Weapon Stabilizer or use of size 1 guardian weapons, but on first impression, it is not game breaking for Titan bomb builds.
btw, I think it is a good choise by FDevs, it open some variety in AX builds for Orthrus and Glaive combat (Ground AXCZ have Glaive), even for Titan runs for large ship with alot hardpoints, but AG Zone Resistance will not break game balance.
Or maybe... is just a new feature for "future content", like FCO and AGZR required to complete some task/mission.
P.S. i got interdicted while using FCO to reach OYA, only one time, but happens.