Picking a stealth class - which one?

With the Angara Avenger, I learned to not do much melee … though you can make it much better (once you get to 20/XX), it's still not great and if you have to melee multiple times, she's probably taking hits … so instead ...

For small critters, avenger strike and shoot in the face with a shotgun. Equip the shotgun with a blade (preferably the heavy melee mod) and short barrel.  Mostly to get her quickly from point A to point B, not all that useful for taking down mooks. 

For bigger critters, stealth grid, avenger strike, leave a sticky grenade gift, one blast of the shotgun and fall back (works really well on Krogan). Strength enhancer booster helps with this.

For bosses, same as with Krogan, but put three to four sticky grenades on the target. Works well on Hydras, Destroyers, plus Ascendants immediately after breaking the orb (don't delay).

Shilesh on the Turian Agent works well with visor to shoot through cover, but the receiver mod* is bugged, doesn't work otherwise, so you're better off with the heavy magazine or even the regular magazine. I use the Agent as a mixed character, both up close, when required on a map and also a ranged character … so typically a heavy weapon and a pistol. I really like "Surfer Dude" … in my head cannon he is the younger brother of the Turian Havoc. He got kicked out of the Turian military and came to Andromeda to start over. She came with him to make sure he didn't get into too much trouble … or get killed.

Note: Stealth grid is bugged. Off host, worst case, it might not work at all. In other instances, it either doesn't cloak your teammates or leaves your teammates invisible to themselves until hit with stealth grid again, or killed and revived, but visible to enemies throughout. If you appear to be cloaked, but you can hear your footfalls, you're not cloaked and bad guys can see you.  With some hosts, it works as intended.  With other hosts, it can vary from wave to wave.

Unlike tactical cloak, stealth grid requires energy cells, so I tend to not use SG for weapon boosts, but instead for objectives, reviving teammates. Definitely prefer TC for shooting stuff … so as an infiltrator, prefer the Turian Agent. The Angara Avenger is a hybrid, use her Avenger Strike, SG and sticky grenades to attack larger targets, use her gun for smaller targets. The AS animation is so long, little stuff typically is dead by the time she gets there, plus the long cooldown … just isn't worth it on little critters … other than to get you someplace you want to be, to do something else.

The Asari Duelist doesn't have stealth. She's a vanguard with a sword (immunity frames during the animation), backlash and lance. Works well with a shotgun and blade. Charge, slice and dice, shoot … generally stuff is dead at that point. Charge is mostly a conveyance to get you from point A to point B, unlike the Avenger, the Dualist is a melee character.  Needs a decent weapon to take on the bosses.

*Originally, I thought the receiver mod for the Shilesh was like it was for the Scorpion and a few other non-penetration capable weapons, where the receiver mod was available by mistake (they fixed this in a patch for all the other weapons).  The last patch came out about the time the Shilesh was released in the game and so the receiver mod was not removed.  But I discovered that the Shilesh could penetrate cover with the Turian Agent's visor.  I tried other non-penetrating weapons with the Turian and his visor … they still cannot penetrate.  So I changed my view.  I think the Shilesh was intended as a weapon that could penetrate, but the receiver is bugged and the mod doesn't work.  From a practical perspective, the only difference is that the Shilesh, in the hands of the Turian Agent, can penetrate cover when using the visor.  Other than that, it cannot.  Either with or without the receiver.  So you are better off using any other mod … a magazine boost, a weapon accuracy boost, perhaps a melee mod … whatever.  Just not a receiver.  Lack of penetration capability is a big reason I don't care that much for the Shilesh … far prefer the Rozerad.

Yeah.

Make sure the critter is not partially exposed. With the "slight" aim correction and a partially exposed critter, you can end up taking something out without actually penetrating cover.

For example, the PAW does not penetrate, but you can often kill a critter behind cover, by hitting the pieces that extend over cover (e.g. shooting an Assember's antenna, sticking out above cover). Since the Shilesh can make minor corrections to aim, you can sometimes do damage arcing over cover. Just not shooting through cover.  I've killed a lot of critters with the PAW on Icebreaker, because even when they are behind cover (the sniper perches), they are partially exposed to the highest sniper perch.

Another possibility … your teammates may be shooting at the same critter, so it is their shots doing damage … if the critter then pops up over cover, you might get the kill and seeing the health bar decline prior to the critter popping up, gives you the impression that it was the Shilesh doing the initial damage.

Without the visor, maybe when the last three critters are alive in a wave, try shooting through a wall, for one of the last critters … without one of your teammates nearby to also be shooting the critter … that might give you a decent sample.  That can be tough, because as soon as the last three are exposed, even a teammate from some distance away might be shooting at a critter.  Zero can be a good map to try that on … as long as someone else is not nearby.