Sorry about the response. I took a while longer to do some things then I thought it'd take.
I've thought about trying a Gunrunner build next time I do a shotty run. Seems like certain classes build certain weapons better. For instance, it looks like the Marine build burst the best since Ammochain eliminates ammo issues. Scout seems to do shotguns best, since between Shottyhead and Gunrunner they can just blast for days without even aiming. Technician seems to do pistols best. Melee is a bit of a crapshoot. Vampyre can be very good at times, but it's hard to pass up the resistances offered by simply having a knife in your offhand with Malicious Blades. I'm sure Blademaster is good too, but I don't know enough about the mechanics of it to understand how :/
I think you're on the wrong track. Rather then certain classes doing certain weapon familes better, it's more accurate to say that certain builds can suit certain playstyles and challenges better.
For example: doing a shotgun run. Keep in mind that cornershooting is always a valid option no matter what class. Scouts would give you the most dynamic playstyle, with access to gunrunner and shottyhead. This would be focused around dodging and using movement to control enemies and spawns and stay on your feat.
Techs allow you access to Fireangel, which allows you to laugh off anything that's an explosion. Which is imps, cacodemons, hell knights, barons of hell, mancubi, revenant, arch-viles, barrels, and cyberdemons. Essentially, this allows you to counteract the damage dropoff of shotguns by simply walking right into the face of a big bad guy and shooting him while laughing as his pitiful attacks do nothing to you. NOTHING AT ALL! MUHAHA!
Marines give you access to Army of the Dead, which changes all your shotguns into armor piercing weapons - greatly increasing their damage against foes with high natural armor or worse, barons that have picked up a unique or exotic armor. This saves you ammo and allows you to cornershoot faster and harder...if such a phrase can be applied to cornershooting.
Three different playstyles and neither is really eons above the other. Of course, if you are locked into one playstyle (for example, you always tank everything), then one class will stand out above the others - because it co-operates with your idea of playing. However, that doesn't mean that any class does any weapon family "better" objectively then one another.
As for learning anything... It's hard to say. I still can't read a mortem very well. It looks like he went with a fairly pure melee build, with a side focus of dodging. I can understand how that works in principle, but not WHY it's effective.
The reason 2dev is manly is because he's a coward. Let that roll around in your head for a little while.
Essentially, the reason that he did so well was because of his movespeed - in that particular run, he got the Dragonslayer, which gives a permanant berserk bonus (60% bonus speed to all actions), but in other runs that he's done he has agility modded boots, armor, and taken as many ranks in Hellrunner as he can. The same goes for his firing speed - if he can attack 3 times with 9d9 before anything can even conceive that he's there, then he can't take damage from everything because it's dead.
DoomRL isn't a turn based game. You decide what you do with your action, but everything is measured in time. The base time for an action is 1 second; ideally you'll want to get this as low as possible. Why? Here's an example:
You have a movespeed of 1 second. You move into the view of an Archvile, which has a speed of 160% = it's base action time is 1/1.6 = 0.625 seconds. The player character always moves first and then the enemies move - so you move into it's view range at the cost of one second. The arch vile then has 1 second to retaliate - with the first 0.625 seconds it charges it's attack, and then (depending on fractional time, which isn't worth going into right now) since you can't move yet, it gets another go and blasts you in the face for 20 damage, knocking you back and leaving you wondering what just happened.
But if you were to have hellrunner 3 (as an extended trait), you would have a 0.55 second movespeed - allowing you to move into the view of the archvile and then plan your next move while it sits there like a derp. As far as it's concerned, it still has another 0.075 seconds before it can even start charging it's attack - allowing you to decide whether to engage it or move out of it's line of sight and find cover.