I've been using the swarm charming technique on mammoths in Icefall as suggested here. The results are very nice but I do get the problem of most of them following me rather than attacking my pet. Would I benefit from spending AA on spell casting subtlety in this regard?

I feel it would but as I solo so much I don't want to spend the AA if I'm wrong.

I can't speak to your actual question but just as a comment, I've been doing gators for weeks, and went to do mammoths last night for the tradeskill impressions, and WOW do they like to wander and flop agro etc. I'm tentatively of the opinion that they're just fickle. I have SCS at R3 atm.

Try to stick with having your new pet attack your old pet.

You'll find that (typically) the mobs that refuse to swarm are the ones you've already damaged down to low health. Those mobs will come after you and ignore the pile on your pet. After going invis and breaking charm a few times, if you are not actually making kills then you end up with a bunch of mobs all at half life and they all just keep pursuing you. At best, you can keep one occupied with pet tank.

Make pet > incite swarm > break charm > make pet > kill old pet > repeat.

You want to keep the numbers of the swarm up, in order to damage your pets down to low life asap, but still you want to keep killing mobs dead (not just damaged). Ideally, you want the swarm mobs all close to full health and the only mob approaching low life is your current pet.

Also, keep in mind if you've got some straggler mob at low life that wants to ignore the swarm and keep pursuing you -- just walk him out of agro range of the swarm and the mob will go snare-dead and stop the chase. Kill those at you leisure.

I'm having this problem as well. I do the gators in Loping plains and typically i'll have say 6 or so Gators on me and I'll charm one (ALL are at 100% and i have only casted Glamour of tunare + ensnare on them) and send the charmed one after another and it will usually end up being just 1v1 gator (even when they are all stacked on top of each other) and the others will just follow me. I have no subtely AA, and this irritates me insanely lol. something i'm doing wrong?

Nah just path the herd pass the 1v1 match acouple times and they will aggro on. And if that doesn't work vinelash cascade is your friend :). A side note to anyone in a position to suggest a fix, could the after effect of vinelash, the snare, no longer overwrite Entrap/Ensnare?

Run in a circle around your pet and their target. Eventually all of the mobs will aggro on the pet. If they don't time a root so that low health mobs get pinned next to your pet, and DoT them down. Storm Strike and Reaping Inferno are also useful finishing tools.

I forgot this post tbh but I did go ahead and spend the AAs anyway. It's definately better now but I'm not sure if it's because of SCS or because I just got better at it.