Every time I pull SMG infil I just get wrecked

From what you described, id say its simply a problem with Infiltrator experience.
SMG infiltrator is about descision making (knowing when, who and where to attack, Where to escape, where to recharge your cloak etc.).
And knowledge of game mechanics (using everything around you to your advantage, and knowing what sort of advantage/disadvantage your target has/is capable of etc.)
The best thing to do (imo) is to just practice playing SMG Infiltrator until your brain gets a "feel" for it. Tips help aswell, but not as much as experience.

Also, i would get rid of ex.mags on your PDW and replace it with a compensator. Then start going for headshots.
If you are uncomfortable or are not confident that you will reliably hit the upper chest area, then keep the ex.mags.

I also have to mention that laser/adv.laser gain very little advantage on SMGs, since they reduce the COF by a %.
Since the COF is already tight, then you wont notice that big of a difference.
I Hipfire with the compensator and do just fine. It reduces the hipfire range a bit, but at that range you should be ADSing anyway imo.

Don't keep a decent distance!
Just get up close, ram some bullets into them and then the next on. Weave through them if there's multiple, it makes them not want to shoot for fear of hitting friendlies. Try shooting off some bullets and knifing them, especially when there's several enemies this can mean you can kill more with one clip.

NNW1?! You should buy NNW4 ASAP!

PDW is rather problematic smg. If you are not PRO you will waste your magazine before kill.
All LR carbines are better then this PDW. So don't keep distance.
If you are playing TR forget SMGs and go Vandal with Laser sight.
If you are NC buy yourself ES SMG.

People tend to dislike PDW because it has worse TTK on blank point, which is the range most infiltrator engage.

PDW is awesone for infiltrator, if you get yourself used to finishing off targets with the knife. the TTK gets fast enough at point blank, and you get yourself the advantage of being useful behind that range.

I got ~3k kills with pdw (and 2.8k knife kills, most of them with PDW). It is my favorite SMG after auraxiuming all SMGs (left it now to auraxium the gold variant of Edriani, and will later work on the auraxium smg though).

My loadout: Silencer + lazer sight + reflex 1x + SPA
suit slot: I granades / andrenaline pump / NW, depending on my mood

If you like to keep your distance as infiltrator - try out the scout rifles, the auto one is probably easiest to use, though I must admit I only auraxiumed it, and about half way with Vandal.

I rarely play infiltrator, but when I do...

I run in cloak, de-cloak, shoot a hip burst to the back of the head, cloak (if I can), swing around their front as they spin to face me and shoot them again with the PDW.

All with continuous movement.

You need to do "strafing runs" like an aircraft at people so your momentum can carry you to cover should things go wrong.

When their are groups of three or more, I will run back and forth through the enemy in a "Z" pattern.

Stoping and aiming really slows down your attack and leaves you open for anyone to shoot at you... even AP lightning tanks... lol.

Silhouettes in this game really stand out, so you want to minimize this as much as possible.

Another tip I would offer is to watch the videos of the "lagmeisters" in PS2. There are a bunch of folks that use latency to good effect. LA's can really use this to their advantage.

A bit cheesy, but its a factor in the game and isn't considered an exploit.