Mercs have healing (that isn't great), but if they use it, their heat goes way up and they're DPS consequently goes down because of the heat problem. Snipers have mitigation from several abilities AND have better resource management. Honestly, I don't see much point of comparing the dummies, all it shows is that a couple of really talented people got lucky enough in the parses to be CLOSE to Snipers. They don't show what happens in the field where it matters. And what's so hard about boosting a few abilities a tiny bit to make it more even?
You're right. To get those good parses, a merc has to basically rely on the RNG. Unload procs and crit need to be friendly with you for that parse. I've had parses with 50+% HSM crit, but 15% unload crit and almost no procs (compared to the average), that parse sucked. I've alos had parses with CRAZY UNLOAD PROCS, but terrible crit % on abilities across the board, that parse sucked. The only good ones, 2900+ are with good RNG. I won't even go into 3000+ range.
Snipers don't need the RNG, their rotation is uninterruptable. They don't rely on procs for their hardest damaging ability, it's always there. (just one comparison).
If they upped the unload chance, then it'd help. 45% sometimes seems like 4.5% on my parses. I go 45 seconds and more without an unload proc at times, and not just once, but several times in a row. It's just either buggy, something related to position, or i'm just very unlucky. I've found that if I have bad procs, and if I move, my procs will come back...but that may just be a huge coincidence.
As for suggestions, lower the CD of electro net to 1 minute so it lines up with other cooldowns. Either lower the cd of power surge to 1 minute or make it longer to 2 minutes so it lines up with cooldowns. And increase barrage proc rate.