Don't let GTAE interrupt. Or don't let GTAE be cast when out of LOS. Or don't let a single GTAE hit half the tower. Or don't let GTAE damage through walls. My point is, the problem is GTAE. Specifically, GTAE from the primary casters in each realm with a 6 second cooldown.
The reason keep defenses are so difficult is because of GTAE. Defenders can't set up well when there's a GTAE that interrupts them every ~6 seconds, and then they can't cast for 3 seconds. Healers will scramble to find locations that aren't being hit from who knows where in order to keep their group mates alive, when they should be able to cast unmolested from inside a closed tower.
This would give all realms a better chance to defend when outnumbered and set up for tower defense, while not changing existing mechanics very much. I have seen (on live) 2fg defend against more than twice their number in tower defenses, on all three realms. Unless it's intended for a single wiz / rune / eld (or worse, 2 staggering their casts) to interrupt a whole tower defense from a very safe distance outside the tower and outside line of sight, then I think we should have a different discussion on that topic.
The reason keep defenses are so difficult is because of GTAE. Defenders can't set up well when there's a GTAE that interrupts them every ~6 seconds, and then they can't cast for 3 seconds. Healers will scramble to find locations that aren't being hit from who knows where in order to keep their group mates alive, when they should be able to cast unmolested from inside a closed tower.
This would give all realms a better chance to defend when outnumbered and set up for tower defense, while not changing existing mechanics very much. I have seen (on live) 2fg defend against more than twice their number in tower defenses, on all three realms. Unless it's intended for a single wiz / rune / eld (or worse, 2 staggering their casts) to interrupt a whole tower defense from a very safe distance outside the tower and outside line of sight, then I think we should have a different discussion on that topic.