It can feel like good gear makes a difference, but still with only certain classes. I just started playing MP on the Xbone last Friday(as some of you know, I normally play on the PC), and here is what I have learned so far:
1) Seabass rules, as always. She was the first character I saved mats to craft (second was Luka). However, low level Sarra still would go down pretty damn quick, since I had no heal on kill I could craft (not even the damn 2% ring

), until getting certain passives. And barrier, of course. Just yesterday I got a unique level 17 staff, with Heal on Hit (can't remember the name), and this has made low level Seabass pretty awesome, on Threatening.
2) Lego as always, is damn near indestructible. Yet due to crappy gear (can't seem to get decent weapons/shields, and he is still in a medium level armor), he has problems at low levels. Shield Wall is a must at all times (learned that the hard way, when trying to change up my build...doh!). He also is a giant snooze fest if you are stuck soloing. That toothpick of a sword just doesn't quite get the job done. Ended up doing a zone five for 30+ minutes.

3) Archer does some great damage even at lower promotes, with a not-totally-crappy bow. But an enemy can't even look at him (except on routine), without him falling over dead. Same with the Hunter. (and I
do love me some bow-men) Finally got my hands on Heal on Hit bow (why is my stupid brain not remembering any of the weapon names!!). This should definitely help.
4) Keeper. I am one of those that actually loves the Keeper with my higher promotes/PC account. She works great with any other player that can truly take advantage of Static Cage (and most of the people I play with, definitely take advantage of it). However, with my lack of controller skills (I use KB&M on the PC), I spend more times doing ill-timed barrier, or missing opportunities to utilize static cage. She fades....a lot. I fully admit the l2p bit, is on me.
5) Reaver might be the best warrior for being under-geared/under-promoted. I can solo her at level one (btw, I don't really
like soloing, but sometimes there is precious little choice), on Routine and Threatening (though there is a fair amount of kiting that goes on, in Threatening, and I did get lucky with the factions). I have an
okay maul (Smash), and medium armor (with upgrades in place). She is the fastest to promote, due to the speed in which she can take down enemies (once she has DR - and I DO have a DR ability ring - was in the first Superb chest I ever bought).
6) My dear Luka is the one that suffers the most with low gear/low promotes. Oh, and I also seem to do a terrible job with the flasks...I keep changing what buttons they are keyed to, to eliminate this crappy playing, but still am "all thumbs". No wait - thumbs are good with controllers. I'm all "pinkies". That sounds about right.
I bring her up, since she too was crafted soon after Seabass (she is one of my favorites on the PC, and used often). Hell, I channel that dwarfy rocketeer! But on the Xbone right now, she is struggling for me to promote her once. *wibble* The worst part is, trying to kill anything with her pocket knives. I have rather poor daggers. I actually was in a group yesterday where we switched to Perilous. I warned them ahead of time, that I would be promoting my Reaver (I knew that once we finished that last Threatening match, that I would reach 20), and the only other character that I had that was in the "teens", was Luka. Even with a very generous player botting with Seabass, I still face-planted. I tried to stay in stealth, whenever I was waiting for the flasks to cool down, but damn....it was bad. Team ended up wiped.
Someone above noted how they played with someone who had got a Hakkon, but was clearly under-promoted. The gear
does help, but I too have been with a player who had Valor, but was clearly low promoted. They took a couple naps throughout the match. They were hitting harder, but without promotes and some game play understanding, they were getting messed up. We were both Reavers at the time, btw.
So yes...gear good, promos even better.