I think DE are supposed to be designed to go along with the "death from a thousand cuts" philosophy. The debate between horde and elite, flexible and specialised is an illusion. DE are kind of all 4, simultaneously. But they're also none of them. What they are are an army in which many units can be reasonably assumed to be able to tackle multiple opponents and in which many units (often those same units) can be reasonably assumed to be capable of specialisation. This results in an army in which many units are able to output a fair amount of damage to a bunch of things. If you want to kill something, you need multiple units and focused fire/assault. Or you can spread your damage around and attempt to cripple a bunch of things.
Every unit is deadly when used alongside other units in the army. But your damage output is diluted throughout your whole army. 6-8 lances spread across dedicated transports do the job of tank-hunting just as well as 2 quad predators, but it's much harder to take out all that anti-tank weaponry. When a couple lances can explode a tank why put all your guns on one platform? This bleeds into the greater DE philosophy in that you have no idea which units are going to die. You know they'll die, you know you spend each unit's lives to get the most effect out of them, but you really don't know which unit is next to die or when. So rather than have one super-specialised squad that is really good at it's job (ala Craftworlders) DE will spread that around 2-3 units instead. And will then attempt to gang up on overly-specialised expensive units to slay them fast, leaving their diluted firepower on the table (or at least some of it).
So DE appear horde-like because they have tons of stuff on the table and some cheap options, but they also appear elite because they can specialise like other armies, but those specialisations are never as good as true specialist armies and they never really have true hordes. They just take 2,3 or 4 guns to do the job of every 1 scalpel weapon from another army. A SM player wanting some more solid AT will take a predator, a DE will take 2 ravagers instead. Tau might take 3 Fire Warriors to fill out troops, DE will take 6, and 3 raiders to boot. Sure the points don't compare but the intent is what's important. DE players tend to have a mentality of doubling everything, taking two of everything, take more. Wanna deal with tanks? Take 15 dark lances. Perfectly reasonable for a DE player. For a SM player 8-12 lascannons might be pushing the boat out.
So the argument of horde vs elite, or generalist/versatile vs specialist doesn't really apply well to DE. They hold to an entirely different doctrine to other armies. They could still use some improvement though.
------------------------------The Bone Flower