My first five masked run was last night and I’ll tell you what I learned.
for me, focusing Iris major was a waste. I always got knocked or interrupted and i don’t have the movement version yet. I replaced this with purification protocol and I don’t regret it. Especially the version that has a chance to KILL an aberration. It’s killed mini bosses INSTANTLY and its amazing and wouldn’t use anything else on a 5 mask run as a major, IMO.
On my hunter I tried multiple runs as BM and SV, both went well TBH, but BM is obviously easier (didn't look at your spec).
Cloak: I didn't even attempt a masked run until I had at least 13 cloak, just wasn't able to power through without enough Sanity loss prevention. One of those masks, the one that reduces total Sanity, really hurts if you don't have enough sanity loss reduction.
Talent Tree: Talking about the one you spend momentos on. If you aren't far enough down, at least with Elite extermination, I dunno if you could even do a five mask TBH. At least not at the gear level that I'm at (casual gear level). Without that talent, don't even try.
ALSO, the last talent in that tree, the Titan one, is AMAZING. You don't realize how much Sanity loss it really prevents until you finally have it.. Holy balls.
I also only drink the +Sanity potions and the Healing potions. If you don't find multiple potions that aren't the sanity ones, i wouldn't drink them as the effects of them running out of time on your character can get you killed easily in 5 masked runs. (this happened my first attempt). I also for the first time used those "K'bab" foods. Very helpful as they restore a lot of sanity over your total run. I definitely recommend.
I watched a few guides as well on optimizing your route, as this helps ALOT. When you first load the map before entering visions, know where you want to go, how much you can pull (mobs that stun and what not) and where you want to stop. This makes a HUGE difference, especially in SW's Mage Quarter.
If you don't have the following things I mentioned, or a really high IL, i would bank your key's until you have either a high enough cloak, or the items I've listed as they basically make or break my runs. With my characters that don't have Gift of the Titans, I can tell a considerable difference. Also my other toons only have around Rank 10 cloak, and it feels 100% worse than my hunter with 15 cloak.
Hope this helps!
P.S. I don't pull AS large of groups in 5 masked runs. Mobs are a lot more dangerous and one slip up and i'm dead. But with the R15 cloak and Gift of the Titans, i can take much more time. I usually make it to the end boss of a 5 masked run with 2 orbs left and Cheat death. Or 3 orbs and NO cheat death. But if you can save cheat death for the final boss, I recommend it. You never know when you're going to flub something up, and you'll be happy you have it for the final boss.