Watching Ramblinnn stream Trials as a Nightstalker, holy crap, that class is busted.
Wombocombo, roll, twitch snipe, roll, twitch snipe, roll, jump, roll, twitch snipe, wombo combo.
I think that really great trials players get miffed when the map doesn't suit their tactics.
I'm no pro, but my own like/dislike comes from a different place: many maps don't suit the mode itself.
You make a good point that individual tactics are biases, but remember that Trials itself is very biased. It plays *very* differently than any other game mode. Snipers for instance are used between 70-90%. The team size is small.
Nobody wants to play Trials on a vehicle map, for instance, even though that would suit the sniper-heavy biases of most Trials players. Many of the Year 2 maps are Rift maps first and don't play especially great for Trials.
So big maps are a pain because they're slow for an already slower 3s gametype. (Frontier, looking at you). Rift maps suck because the lanes are designed for running, rather than pure combat (looking at you, Memento). Maps that are small aren't always great either when they're too constrained and combat feels repetitive even within a single match.
Exodus Blue is a great example. It's abysmal in 6s. It's the prototypical Mayhem map. You're always being shot at by 6 people. Meanwhile, it's great for Trials because there's no downtime between spawn & finding the enemy, has a good variety of open and tight places, and has lots of options for movement.