Hmm, I tried this and kept getting melted by Mida. also from a comment on reddit everybody in Trials is using Mida too. and that's the best indicator.
I think it's baloney I bet Mida is going to get nerfed quickly, due in part to community outcry, yet that same community was hunky dory with Palindrome and Eyesluna (same gun different skin really) being the only viable top tier primaries for like a year (literally).
Trials has a different flow than Quickplay or even your typical Competitive match. There is a lot of distant coordinated teamshooting... it's very passive. Therefore scout rifles were dominant.
The map was also a scout rifle-friendly map... it was pretty much a must, and there are more limited options for scout rifles in the Energy slot (or at least they're harder to get), so loadout comes into play here. The only 2 good/decent scouts in the Energy slot that I've come across are Manannan and the Trials scout is decent.
The most common loadout in Trials that I saw was MIDA + Uriels and/or Prosecutor (Trials AR that is similar to Uriels). MIDA + Mini was a fairly close second. This is solid loadout for PVP in general, but especially for Trials, and it's easy to obtain these weapons.
So with that said, I don't really think MIDA is overpowered, just a very popular weapon because it's familiar to a lot of players, is fairly easy to obtain, and easy to find an energy weapon to pair with. There are other scout rifles that can easily go toe-to-toe with MIDA, and inside midrange, Uriels/Prosecutor (or even a good 600RPM AR) will outgun a MIDA more times than not IMO. It's easy to stay within this range too, because most of the maps aren't very big.
So both Uriels and MIDA are top-tier PVP weapons, hence why it's a common pairing.
Here's a list of weapons I've tried that I think are solid for PVP:
Kinetic SRs: MIDA, Nameless Midnight
Kinetic AR: Origin Story
Kinetic PR: Nightshade
Kinetic HC: Better Devils, The Old Fashioned, Judgement (Trials HC)
Energy SRs: Manannan, The End (Trials SR)
Energy AR: Uriels Gift, Prosecutor (both 450RPM), Martyrs Make (600RPM)
Energy PR: Nergal
Energy HC: Minuet, Annual Skate
Energy Sidearm: The Last Hope (or most of the Omolon burst Sidearms)
I've also heard good things about 600RPM SMGs but I haven't been fortunate enough to get one to drop for me.