I might be handy to tell your general strategy with this list.
I don't think this list is really competitive for the following reasons:
1) Archon is really too expensive, sure as long as he rolls 2+ he's fine, Husk Blade is a very big investment, I personally use Electrocorrosive whip to get the best of 2w IC.
Haywire Grenades aren't really necessary if you can double you strength multiple times.
2) You only have 5 Skimmers, these will be blast to pieces very quick, you don't take the SC upgrade on venoms, which is really one of their best features.
All these foot slogging models, they don't fit in a non WWP list. In 5th you need the speed or you don't have much contribution. You could have one foot-slogging unit to come out of reserves to claim you home objective but otherwise it is a long walk and T3 and 5+ save isn't going to help you survive long enough.
3) You never bought the squad leader upgrade, this is very bad for leadership, at least wyches and wracks shoud take this option, hydra Gauntlets are a cool model but rule wise not that cool.
4) Incubi are very cool on paper but you should note their squishiness, best to use them in a squad of 4 and add an Archon with PGL, they lack grenades! If you take too many they will chew their target and be out in the open, even 3+ save with FNP isn't that great these days on T3. There are simple too many ways to kill them effectively.
5) Mandrakes, they suck without the pain token, so I reckon the Heamy joins them? There are still a sub-par unit.
6) Reavers can be cool but I find them too expensive for their survivability. They might work in a list which puts a lot of pressure on the opponent so they is no good choice for the opponent to shoot. So a mechanised list.
7) 13 Darklight weapons doesn't pull it. You should read
this thread on list constructing. It really pins down some major points.
8 ) Talos on foot isn't really fast enough, I tried a list with two and they didn't see much combat. The TL-HB is really too good to pass on and run but this gives your opponent enough time to ignore it just long enough.
It's not that only one build can be competitive but you don't have enough Ranged Haywire to claim it to be spammed: you should look at Scourges for that.
Just take a look at some list from Gardeth or other players who have success at big tournaments to get an idea on what works in competitive environments.
Personally I find venom spam shooting with some counter assault most effective. I used to play wych cult but they lost some of their cool rules and most specially they have to close the gap with the opponent real fast and this prevents them to use one of our greatest upgrades: Night Shields. It took me a while to take them too on my vehicles but now I've seen their power again, in combination with FF, it is awesome to see opponents come to you!
I must say Wyches with an Heamonculus can make a hell of a tar pit unit but not much more than that: they kill of enemies very slow, only Painbringer drugs changes this. My new first choice are the wracks, together with they LG, they kill of so many enemies, you should add the haemy to give them Furious Charge at the start, very scary for T4!