Like someone said, try to attack the same target as the tank. If you are playing with a good tank, he should mark the targets with signs like (1), (2), (3), etc. In that case, it is easy: kill (1) first, then (2), etc.
I don't bother marking targets anymore since A) I'm not going to lose threat and B) It's fairly easy to attack the same target as the DPS / AoE anyway.
It goes by pretty fast anyway and I really don't think there's that much room to pull more than 1 group of mobs at a time.
Can pull the first three packs together and blow your cooldowns here since you don't need them for the boss. Then there's the pack + whelps (and if you're adventurous, can just take it down the hall to the first Haranguing pack). There's that odd pack before the cannons that I usually just solo pull since the Haranguing ones make for awkward grouping. After the second boss, can pull everything to the Wyvern lockout and then the final pack is done solo.
Can split the first pull and the post-second boss pull if Healing / DPS isn't there. Basically each set between bosses can be done in 1-2 pulls instead of 3-4. I usually just check my Healer and whatever AoE DPS we have to see if they're probably up for the damage output (and then yolo pull it anyway).
...but, yeah, it saves all of like a minute or so unless you get a really good group. Even doing each pack individually, its like a 20m dungeon so I mostly just do it because I like tanking all the things. And to actually get to use Hallowed in dungeons.