Definitely been my experience as well. Expeditions as currently implemented certainly railroad you into particular playstyles. I never really touched blighted rounds in the main campaign, preferring a crit sniper-focussed build, but expeditions make that build pretty worthless. Too many fast-moving targets from all angles, and some arenas totally lack cover.
The thing is, I still take that sniper rifle as a backup gun and the 300-500k crits I was getting with it would still be great in the right circumstance - but the loss of blighted rounds on switching weapons makes it a total no-go.
Ridiculously overpowered set bonuses is something I’m glad to get away from after Diablo 3 and I don’t think it’s a problem per se. However, the bigger issue is that since rolls on legendaries do not appear to be random, you’re forced into trading off against well-rolled epics. The three piece bonus is just not worth working towards when you’re losing essential mods and e.g. the gloves will never have ‘bonus firepower’ as a stat.