Clearing the whole zone was for grinding AA and item xp. How would you rather grind out AA?
[Using a SK/Rog/Wiz] It took at least 1000+ AA in THJ in order to clear everything but that last boss or three. For example, I started mostly in Velious. At max level and ~500 AA, I could not kill most of the dragons in NToV, nor the end bosses in giant or dragon city. The final boss of the Xpac was Sleeper, a custom made boss by THJ team; I think I needed ~1500 AA in order to kill him (plus a decent amount of upgraded NToV gear).
[Using a SK/Brd/Wiz] For grinding, at ~500 AA, I could not kill all of Dragon Necropolis at once. I had to break it into at least 4 or 5 pulls. At ~1000 AA I could pull all of the top in 1 pull then all of the rat tunnels in 1 pull (DN was too buggy to try to do the whole zone, imo). By the time the rats were mega crit nuked by Wiz buffed Bard nukes, the top was respawned, so off to do al that again.
Would you rather march through Dragon Necropolis killing a few mobs at a time getting 1/20th the XP rate? That is somehow more fun? That is going to be the zone where mobs give the most xp per hp, so if you want to slow march through somewhere else, it's going to take even longer.
I don't remember the actual time spent, but grinding XP in Velious didn't feel like it was taking that long or being overly tedious. Once I could clear Sleeper, I didn't grind XP until Luclin and found grind spots in Luclin to grind item XP. Plane of Fire is where I could pull a massive amount of mobs (~60% of the zone) and burn it with Bard/Wiz synergy in ~3 spells. I still split it into a front group and a back group due to the game crashing while trying to process all those crits at the same time (Wiz spells would crash in PoF, but bard wouldn't). Since AA was all farmed and I was only doing it for item XP, it became enough of a drag that I decided to end PoP and wait for LDoN, even though I could not reliably kill the last 2 bosses (1 being a custom THJ boss).
Edit: Most zones were not being mass pulled and those zones that were, didn't usually have bosses in them. The three zones I mass pulled were DN, Umbral Plains, and PoFire (many people did Chardok too; Vex Thal was too buggy to do reliably). The instances you could spin up with bosses in them had long cooldowns.
