I've been experimenting a lot with melee huntress build courtesy of tjbearpig. It works quite well with cyclonics IV on gold and reasonable lag off host. I can get killstreaks if rushing a spawn and using crusader with drill ammo. Also, it looks like it ignores phantom's bubble and damage resistances. I've just had a game where I was able to send two bubbled/flipping phantoms flying across the map with one melee.
Also experimenting with human adept melee and it is substantially more tricky. It does more damage to armor compared to huntress but does not reliably one hit kill shielded mooks on gold. I still have not figured out completely the distance and cone angle. IMHO, this build is quite difficult to master properly especially off host. I'm not sure about force as well. However, it does stagger phantoms.
Although both builds are extreme fun.
Venom seems to be the best choice for most non-krogan melee builds. The only negative is that it kills mooks too quickly, so you miss out on the ecstasy of a true melee kill. This is especially true on infiltrators and a good reason to take cryo or explosive ammo instead of distruptor.
The phantom bubble resists all melee, but the asari animation is so long that you're probably catching them after the bubble's effect has worn off. It is so nice to send them flying though. I hung one in the low rafters of reactor once.
Brutes are the absolute best targets for her melee. About 2 seconds of cloaked DC are enough to let you kill them with a single melee attack.
Shockwave is situationally useful. Singularity not that helpful. I die quite a few times on later waves depending on a map. The melee animation can be sometimes cancelled before it actually finishes as damage is applied at about 3/4 of the move but for me, it is a bit tricky to catch the exact moment.
The human adepts melee is definitely challenge off host. Again, strategic venom shots help a lot. Cryo's slow effect can be a big help here, though the adept really benefits from distruptor's shield stripping ability and a nearby singularity.
Make sure your singularity setup includes 'radius' and try to avoid casting it a targets that can dodge. I usually aim for the spot I want to melee from, trusting that the target will meet me there. The stagger and lift effects let you get into melee range or soften the target with a Sing/Shock combo. It also takes out swarmers, which can suck up your melee's 3 target limit. Lol doing 3k damage to swarmers while the ravager behind them is untouched. Biower, pls.
The human adept has one of the few non-locking melees. Use this to your advantage. It's also pretty fast, so 2 successive heavy melees is feasible. Especially if your singularity is still staggering.
For all low shield melee kits, be proactive with your Ops Packs. I usually hold them until wave 6ish, and then burn them right before I engage 3 marauders or a ravager, scion, etc. Likewise with Medigels, using your first 4 tactically in late waves to stay in a melee fight is smart*. Smoke 'em if you got 'em.
*Except when in range of a sync-killer or against geth, who can stunlock a reviving character like nothing else in the game.