The troll's need to reset when you exit the scene so you can repeatedly enter and exit to kill them like you could when they were encounters. Not even worth using the zone anymore with it's current setting unless your just there for the buff.
For me, I entered the scene, killed both trolls. Then harvested everything and killed the remaining creatures. Exited scene. Re-entered and it was reset.
I think you've hit the nail on the reason why this was changed to begin with. I assume you can still flip it with a second account like so many people do.
There wasn't enough spawns for the people who wanted to kill them. There was usually a waiting line in the pass. If they leave it as it is now, they are fixing a problem with a popular activity by making the activity unpopular lol. No one is going to farm out the whole zone or wait 5-10 mins for a respawn when all they want is the chance at a ring or the troll stuff. Doesn't bother the bots though, they can keep doin it. Same with people who can find a workaround like you mentioned. You should be able to kill these things all day if that's what you want to do. Same goes for dragons and similar mobs. The drop rates are terrible by themselves and that is coupled with needing a bunch of them to upgrade to higher tiers. Adding these artificial wait times just turns a fun activity into something not even worth doing. Also they have allowed ppl to do this for an extended period. So if you got your stuff already, great. If not, sol. It was reasonably fun going in there and killing these things for a bit. At the present settings I don't even bother with it.
I don't disagree with any of the above. Just offered an explanation for why it was probably changed. I gave up trying to get that troll encounter a long time ago, troll was never up and there was usually a bunch of folks waiting to nab it. I just added it to the list of pointless activities and moved on. Sadly, there's enough people who would lodge an alt in there and flip the scene all day that they could farm it constantly - as you say we should be able to do - but only if you were willing to use these methods. With it being a static scene, absolutely nothing is going to change in that regard, except that if you are trying to go do it once a day it will be available without the wait.
Well They change the respawn, the issues are resolved for both crowds. Larger issues they can worry about if they decide to tackle the game as a whole
If you want to kill tons of trolls, you are aware of the very fast spawning troll in Vertas Pass? For me personally, I now can enter this scene any time, kill the trolls, get the toenails, and harvest all the resources. Works great for me.