To be fair, with a Latios waiting in the wings, you were kinda screwed no matter who you sacked to get rid of Heatran. Heatran kinda has you covered in general, it seems like--Megabro needs to be at least a little set up to deal with most of its sets. Everyone else obviously gets blasted (Pheromosa) or has to trade shots (Xurkitree).
I just got through another run up to 83. I can't upload the battle video, but the enemy team was froslass/exeggutor/amoonguss.
I ran into heatran a few times on the way and it really wasn't that bad. There are actually not many trainers that can even have the scarf set, going by serebii. All the other sets die horribly to all-out pummeling, so it usually just died horribly when i ran into it. The scarf set is normally set-up bait- it's going to pick a fire attack vs phero or ep vs xurk, and the highest bro should ever take is 40% from either. The stat drop was unfortunate, but eh. The one that ended this run is a much bigger flaw.
In general, grass/poisons kind of wreck me. iB from phero doesn't do all that much, hjk is resisted, and u-turn abandons a sub if i have one. Xurk's only neutral move is signal beam, which is the same as a resisted tbolt almost. Basically all of them have recovery or status, which makes matters worse. I wish i could run psychic on bro, but psyshock is the only sure way to beat enemy CM, and slowbro is rarely going to outspeed and can't ohko.
I was worried about venusaur, but I somehow never ran into the mega on my way up- as a lead, i imagine it would sweep me unless i got a lucky status in. I saw the salac set a couple times, including at 50, but uturn does half to it so it was really not too bad. Shiinotic was total garbage to deal with. One of the sets has weakness policy, so you have to play around that with phero. At some point i got slowbro out on it and it spammed sap strength on me until i was at -6 for no good reason. Obviously amoonguss ended my run, so it's probably my least favorite. I don't think there is anything i could change to beat it, unless slowbro can net a kill with psychic amd outspeed with the right evs. Tangrowth is also pretty bad, but power whip actually does less than half to slowbro, so as long as you start from full you can stall for a miss with slack off. Giga drain is relatively weak and i don't think the whip set has sleep powder. It also dies a lot easier to phero or xurk.
Ghosts are also pretty annoying, but none of the ones i saw really scared me much except marowak. I saw decidueye, dhelmise, trevanent, and gourgeist a few times and they all basically did nothing. The funniest thing was setting up sub on phantom force dhelmise. Froslass is annoying with a possible miss chance, but doesn't really have offensive chops. I should've set up slowbro on the one in the last battle, but i was able to take it down without losing anything so i got cocky.
I almost lost to the mono-electric veteran just before the end. Electric spam stops slowbro from getting set up, and xurk's coverage mpves are decidely ehh. Best-case is phero gets a sub up on a twave, but a good chunk of them are all-in offense and the fliers are juat plain annoying.
I think i'll do one more run with the team as-is then look at the possibility of special phero. In 3v3s you probably aren't going to need your fighting nuke more than once very often, and ice beam was getting a lot of use. I liked having a powerful uturn, but it's more for chip to help out xurk with a ko than for coverage. Fightinium gets a 100% accuracy attack either way. The big problem is that it makes the team fully special, which is pretty bad overall. I saw regice a few times on the way up this time and chuckled, but with special phero it might be a pain. They all run bolt or thunder, so i'd have to run calcs to make sure i have an answer.
