Epsilon is Canyon is intresting case. Yes it's lethal as assults often go there, and for that reason, I often try to go there in an assult or applicable heavy. That map is too mazelike for most of my assults, so I just want to get easy clean fight by going againts enemy assults. Then there's zero risk to get suprised by lights.
It's not even too hard to get on top of the fight at epsilon, just peek from the corner slowly, don't walk too far, and don't do it if other assults don't follow you. And once you get upper hand, push hard.
Theta on frozen river is so horrible. Yet so many people go down there, worst off in an assult. I often try to warn people about it, maybe sometimes it works, but clearly many times not.
I don't have a problem when the enemy does that. Most likely I can take advantage of it. A friendly heavy or assult goes down there, oh-no.
Fresh example from today, I warned.
Enemy Kodiak goes down there to die, good. So does friendly Kodiak, bad. Most enemy assults went over to the other side of river, that's pretty unusual, usually just few lights cap those two bases that side.
Both end up with about 200+ damage probably fighting each other and dying to long range weapons after that. That enemy King Crab had a little peculiar long range config, but seemed to work for him. I recall enemy Awesome also had long range too, and our Dire probably had lots of UAC, can't remember. That surviving enemy Commando managed to surprise me late in game, not damage too much though, but then as I chased him, I was taken out by that King Crab.