From a Fluff perspective and a Gameplay perspective should Dark Eldar have Titans?

[Fueldrop]

Void Mine? Scatterfield Missiles? Doesn't let you loot a whole lot of stuff either.
Also if your target is heavily defended you need something to break these defence. You are not like "oh... ok.. I guess we just go home now and forget about that".
The current solution is: "Wait a second I call our pansy cousins to crack that door open"

Void mine = Lance. Blast.
That is wrong in every way imaginable. I mean... HOW?!?
Missiles... yeah, you have a point there.

If the target is behind heavy fortifications, go for an easier target or failing that webway in. Going after a fortification is a very poor risk/reward ratio most of the time.

The problem isn't that the DE need titans. It's that the DE need firepower period.