Why disable heals on gates? what's wrong with you? Disable Chiron in siege then since people use them to fire through walls and gates? Disable hide since it's unfair to others ( this one i would like to see), heck let us have people with carpentry skill be the only one to be able to fix gates? why not?
Another one of your meaningless comparisons. Bleeding was giving an alternative for a current problem in siege war. Instead of players healing gates, have siege engines that can do so. Yet your argument is that warden pets can attack threw gates, and that rogues have a skill called hide, so players should be able to heal gates?... just... wow.
Agreed with BB, however capping down to about 20 seconds, though fearless capping would still be doable by some classes, it would be very difficult on a well trapped tower.
As for the healing on gates by players, disable that, however also disable player damage to gates, not that players really do much to them as it is. However if it takes 5 people 5minutes to take a gate down 10%. A healer/knight shouldn't be able to walk up and spend 1-15seconds getting it back to full.