The single shot rifle as main for sure and then an LMG for the busy times.
I have a sniper for situational purposes but don't use it much.
I'd keep a shotgun for those surprise moments but honestly the time it takes to switch out weapons I'd be better off keeping the MK and shooting.
Maybe they should fix that.
Playing mostly solo, an assault rifle in slot 1 (I'm partial to an M4 with extended magazine, but I like a few others too). Usually an MK17 rifle in slot 2.
I've tried LMGs and SMGs but don't particularly care for either, as I usually engage at medium to long range. Marksman rifles are okay, but I prefer a regular rifle in most cases.
I use the M4 almost exclusively, since I love the sound it makes, other than when I know I will be facing alot of difficult enemies like in a landmarks. If that is the case, I put on a LMG as secondary.
I used the MK17 rifle alot until world tier 1, It just didn't seem to keep up with the damage that well.
LMGs are once again the best archetype for pve right now (same as in div1 at the beginning).
there isnt really any good reason not to bring 1 LMG with you at all
you could make an argument for very few assault rifles, but they lack the ammunition capacity and accuracy of an LMG.
as a second weapon i like to bring a marksman rifle just in case i need some burst-dmg or dont want to get close to something.
I'm lvl 22 currently, and i'm using M700 with 8x scope (+35% headshot damage, -accuracy) and USC .45 rifle with extended mag (+12) and all +stability mods i have for close combat. Also, Double Barrel Sawed Off as a sidearm appears to be super-effective against melee enemies. Unfortunately, i found only one on lvl 15, and now it's underleveled, so i have to use M1911 instead.
By the way, does anybody know where to find Double Barrel Sawed Off blueprint?