i have good luck with jj el84s when i was running amps that used those tubes. there is a low output version, do not get that for your amp
There are more than one version of the JJ EL 84's and some will fail in a Mesa. You are dead on that the low output version is one to be avoided.
The larger bottle EL 84's like the old TAD and in particular one version of the Tung Sol EL 84 have been the most reliable for me in these amps.
These Mesa amps that run EL 84's are all brutal on power tubes. I have run them for years, but as of now have my F 30 combo on Marketplace because of this. You absolutely must run a robust EL 84 in these amps, or you will have issues and most of the time sudden issues with failed power tubes. It's not a maybe it will happen, and you also have to replace the power tubes in these if you often gig with them. It just goes with the territory. The Simucast EL 84 Mesa amps sound great, but because of how they are designed, run the power tubes very hard. I own 3 EL 84 amps right now, and I am selling the Boogie because I am simply tired of dealing with this. Have run these amps for many years on stage, though.
Going to a PRS Sonsera 20 that runs a pair of 6L6's for now, but I am looking for a first gen US built PRS Archon 25.
Get to a reputable tube vendor and tell them what you have, then let them recommend the right set of EL 84;s is my strong advice to you.
There is a set of the JJ's that will live in these, but a few other tubes that will live and sound much better.
Or you can just buy a set from Mesa. I would buy a quad, not just a pair of whatever you get so you have a back-up pair.
Here are the Mesa EL 84's and I like them better than the JJ's but not as well as the bigger bottle Tung Sol or TAD tubes. Here is a set of the Mesa EL 84's from Reverb.