Dealing with Eldar?

[Drannak]

So I'm no stranger to DoW at all (played and beaten all of them multiple times) and something thta has ALWAYS bugged me with DoW:SS is the Eldar.. I'm doing the campaign currently, as Necrons, on Hard.... It's so very pointless, annoying, and time-wasting that I can destroy their bases within 15 mins.... and then spend another 30 with my slow-ass army roaming the map playing "find the last webway assembly or little building tucked in a corner way the ♥♥♥♥ over here" because it counts as a unit-producing building, therefor no victory till it's dead. Like, first conquest, destroyed their base at 14 mins on timer.... finished the mission at 31 mins and some change because there was a single webway assembly on the other side of the map and it took me forever to check everywhere. Any way to deal with this faster?

[76561198200638999]

Scarabs detect.
Wraiths detect and can destroy weak buildings pretty fast if you have a couple. Be sure to upgrade them so they become near immune to ranged damge too (like 80-95% resist).
When you move your camera over an area where there is a cloaked webway gate, you should hear the sound effect it produces. This pretty much makes the cloak useless against humans.

The way Necrons deal with mobility issues lategame is the Deciever. The Illusionary Monolith:
1) Can teleport.
2) Can be used as a beacon for teleportation of Warriors, Immortals and Flayed ones, just like the real Monolith can.
3) Can be summoned over an INSANE distence from the Deciever, who himself can jump really damn far and has 2 jumps. Plus his "jump cooldown" is seperate from the Necron Lord.
So you can jump to full extent with the Lord, then turn into the Deciever, jump 2 times again and then summon the Illusionary Mono and after that transport your immortals and warriors blob right into the heart of the enemy base. You hop from one end of the map to the other like that easier than any other race, other than maybe Space Marines.

[Drannak]

Detecting isn't my problem, it's that extra wasted time it takes to scrounge around the entire map to find that one webway assembly that the NPC decides to build in the middle of nowhere, or the HQ they started the MOMENT theirs was destroyed, but their builders died and couldn't reach it to finish it, or something dumb like that... This wasn't an issue in Dark Crusade as the vic condition was Destroy HQ, not Ahnillation... helped a lot with time.

[qrosa]

there really isn't any special trick, and you kinda answered your own question already: fast units!
if you know or feel like all they have left is some lone (unfinished) building somewhere, just spit and spread out destroyers, wraiths and builder scarabs.
but even then, it's pretty annoying, and there's no way around it since this is how they decided to code the AI.

if you have the units to rush them early on, go in deep and focus the builder units, it may save you from a headache. :-) of course, the necrons are not exactly the best race for this, but an upgraded necron lord can do some serious damage by himself.