That's the whole point though as to why factions were randomized, if this was implemented into public lobbies than everyone or close to it will be choosing demon factions. Example: most pug hosts these days have farmed hakkon weapons by setting fc nightmare to frost and will most likely have an elementalist in the group to due to fire weakness.
The only thing that randomizing factions accomplished is to avoid balancing factions. If they can't be bothered to balance factions according to a common factor for a set difficulty, what are they doing all day?
Wavebend is right in saying there's a clear line as to what factions are easier and whose are harder.
Quinari > Darkspawn > Red Templars > Venatori > Demons
The Quinari are by far harder than Darkspawn because of their multiple immunities. They also have a lot more HP and Damage than they should. There's something very wrong when a Saarebas survives 8 Spike Trap at 9K each while shooting with a Hakkon Bow for around 5k (3 shots x 1.7K) in-between traps...
The Darkspawn are much harder than Red Templars because of their HP and Damage. The Bolters on Wave 4 were overdone a tad too much. I don't mind them, but they shouldn't be in such numbers to pin you down like they do. It's not normal someone at 80% range resist with a Lego can go down in less than 2 seconds if he doesn't have Walking Fortress active...
Red Templars are "hard" because of their range but compared to the 2 new factions they're toothless.
Venatori are still a lowly copy cat of the Red Templars. Everything they do, Templars do better. Except maybe locking you up between mines and Shield guys. I like how they diversified them with mages. I hate mages, I hate getting 32 mines under me in less than a second and insta-die, but I do like they made them somewhat balanced at relatively the same level as the Red Templars.
Demons... well I still don't understand why they're so weak. They've always been weak, by a very very very large margin at that. The only "difficult" thing about them was the Demon Commander, but now he's been "rectified" as he was ridiculously OP at the beginning. Sadly, the rest of the faction wasn't buffed to compensate. And when I say they should buff Demons, I'm not saying they should add 40 Despair demons... I think they should concentrate on the low tier units, when is the last time a Wraith (normal, cold or electricity) ever give you any trouble?
If Bioware doesn't want us to chose a faction, then they should at least have the decency to balance them so they are on the same level. Right now, we have 2 very OP factions and 1 very underpowered faction. The Templars and the Venatori are the most balanced in my opinion.