Quite honestly, it's always been the main shtick of the warlock to be an at-will blaster, with a minor bit of utility added in. They're not really "spellcasters" per se.
In 3.5, Eldritch Blast was a class feature, and their main one - most of their invocations involved tricking it out to do various things.
In 4E it was an at-will power somewhat poachable by other classes, but warlocks didn't have a choice in taking it - they received EB just by being a warlock and then their Pact dictated their other at-will power. A warlock could adjust their secondary specialty by deciding which pact to take (and actually do passably well at "faking" a different role), but they were still primarily single-target ranged strikers/blasters. It wasn't until later in 4E that the Eldritch Strike at-will was released and you got the option to build a "bladelock" through choosing either EB or ES. Most of their encounter and daily powers from the various Pacts were pretty blast-y as well and continued to reinforce the striker role.
I'm still not convinced that Eldritch Blast shouldn't have just become a class feature again in 5th Edition, rather than a cantrip... (It would solve most of the issues with it.)
In any event, although you can certainly build a warlock to do a lot of different things, I firmly believe that the main combat tactic of the warlock is meant to be to use their limited spell slots as a facilitator (through defense, deception and debuffing) to enable them to get their at-will damage on.