Wireframes are good, but only if you can target / or hit the vital areas.
eg: on the templar it takes less time to just to pour fire into it.
on the avenger just shoot the tail off and it's easy.
The reason:
the templar's shield is mounted under the tail and it's really hard to blow it off.
the avenger's tail has the shield, the thruster and the turret mounted on it (think it also has the CM and mine dropper on it too).
Blow the tail off and it can't thrust away from you, it can't shoot you when your behind it and it has no shield (and possibly, it can't use CM's to avoid missiles or drop mines in your face).
I found all this out by attacking them in a wyrm LF. If I used a VHF then it wouldn't be a problem, I'd be able to blast them fairly easily.