First off, it's slow. Dangerously slow for a Dark Eldar Army. If you are planning on walking these across the battlefield, missile launchers will eat you up, as you only have 3 wounds. It's hard to get pain tokens into them until they get into close combat. While I can see someone using a talos from the backfield, I think they are strongest from a warp portal. It also guarantees that anyone that tries to block off your warp portal will pay dearly when they are unsuccessful.
Lets look at them. WS5 BS3 S7 T7 W3 I4 Ad6 Ld10 Sv3+ . They are fearless, have power from pain, move through cover and are a Monstrous Creatures. You can replace their close combat weapon with a twin linked liquifier (nice but might kill to many and preclude your charge), inchor injector (instant death) , or chain flails (roll an extra d6 and pick the highest). You can then take an extra close combat weapon.
Weapon wise you come with a twin linked splinter cannon. Remember you are a monstrous creature, so you are relentless. You can replace the splinter cannon with a stinger pod, twin linked haywire blaster, or a twin linked heat lance. The twin linked heat lance seems the most reliable. Gives you a chance to blow up a close vehicle and then chew on the crew inside when you charge them in assault.
Set up wise, I will be using these with the twin linked heat lance, extra close combat weapon, and chain flails. I suppose if you plan on a defensive talos, you can always choose a longer range weapon like the splinter cannon. While I like the idea of the liquifier, I don't like the idea of killing too many guys and not being able to assault.
The Talos shines in area denial, with 3-8 attacks on the charge. 1 for charge +extra close combat weapon, and 2d6 pick the highest random attacks. With S7 I4, you should be able to do pretty well. If you remember that your talos is a Support piece they will excel on the table top. Alone you will see them killed by meltas and missile fire. However get yourself a pain token and you will reduce those kills to just meltas, as Krak missiles you will get a Feel No Pain save with your first pain token. Plasma will also be rather dangerous, but this is why you are a support piece, and not the apex of the assault.
Come out of a Warp Portal for field placement, and use these in conjunction with other close combat units. A Talos has a 6" movement and 6" assault and is not fleet. So they have reach of 12" from any portal when you are trying to assault. A portal centrally located gives you 24" dia reach (12" in any direction) from the portal. Your portal is 3" diameter, so basically you can draw 27" diameter circles on the table top and that gives you how much coverage they have as they come through a portal. From the center of the portal 1.5"+ 6" movement + 6" assault radius. The idea is to show how much territory on the board a talos can threaten if you placed one or two webways.
Pain tokens means the Talos will get better as the game proceeds, so they work well with Cronos Parasite engines. FNP and Furious charge make them true monsters. S8 with I5 on the charge with 3-8 attacks/ avg (6). Wow.
You will find that your forward assaults will get that extra push with a talos or two in the ranks. If you read the blog, you will see that I have them in a current list I am using. However the Talos is backed up two Cronos Parasite Engines, a unit of Incubi, and a Ginsu on steriods (archon).