I will say this, I think personally that SMN is one of the best classes for Sunken Temple of Qarn and is a solid option for Aurum Vale, and here is, in my opinion, why.

1) SMN should not be the one doing the adds on final boss. Adds should be done by one person to prevent wild hate and not landing the boxes on the tiles. This is best left to any other dps. Can SMN do it? Absolutely. But you are better served getting the boss down so you get past the add stage sooner (adds quit after 80% or three/four adds spawn total).

2) Titan can tank this fight incredibly well, believe it or not. When I ran this as a Paladin with a SMN, I was the one on adds and let Titan tank the fight (used Sic, then manually placed him against the far left well and between the occasional Sustain and Cure, Titan has quite a bit of enmity + innate damage reduction. I was always ready to Provoke and tank should it be necessary, but give titan a few seconds to build up and at that level, it's hard to take it from him.

3) SMN are capable of handling the Mythril Verges, but this is better left to other DPS. You just want to be sure you're getting Bio II/Bio on asap since you deal your damage in tics and not immediate, you'll need every bit you can get. If you aren't Titan Tanking it, use Ifrit for higher dps on the verges.

4) During the dungeon itself, whenever you come up against a bee (especially two) then let Titan tank one of them. This way Final Sting kills Titan (easily resummonable) and not the tank (not quite so easily summonable). This is helpful during the first boss, so boss handles one bee, Titan handles the other and makes it much less stressful on all. (Also, load boss on DoTs then Bane them onto the two bees and they'll often die before Final Sting can come up)

5) SMN DoTs (especially Miasma) help taking down the treasure box easily. Remember to call back your pet so he doesn't pull the group before the tank is ready, but popping Bio 2/Bio and then before you think he's going to run, Miasma to slow him down and keep the DoTs ticking will make it easier to kill the box or have it so weak the next encounter it will die to one hit. The best strat for the first time you see it? Have Titan attack the Bee so everyone can focus down the box. Titan takes the bee with him and you get the loot, all to the good!

Aurum Vale you don't have as many tricks, but loading Miser on DoTs, then Bane will put them on a good number (3 of them) so that helps. But you have a secret weapon here I rarely see SMN use, or even know about, and that is Tri-Diasaster. Once whatever fruit spawn into seedlings, Tri-Diasaster them. This will root them in place, so then the other DPS can just focus them one at a time and if they have a stun (MNK, DRG) then you won't ever get hit, and can whittle them down before focusing back on the box. Do NOT AoE them (except for a Baned Bio/Bio2) or it will break the bind and be useless. This alone makes SMN a worthy bringer into AV.

Just my opinion, hopefully this information can help you out because I personally enjoy these dungeons on my SMN.