SmiloDan wrote:
Giving them an invocation every level makes them more versatile, but it doesn't increase their action economy. And it lets them both increase the effects of their eldritch blasts (essence and shape invocations) and let them do some interesting non-eldritch blast stuff. With only 12 invocations over 20 levels, it made warlocks one-trick ponies (well, 12 tricks, but you get the idea...).
Compare them to sorcerers. Sorcerers get double to quadruple the spells known, and their choices are a lot more versatile. There are only a few dozen invocations to choose from, and on 12 or 20 known, depending on which version of warlock is used. Granted, warlocks can use their abilities at will, but their abilities are generally weaker than the sorcerer/wizard version of their abilities (Flying at speed 30 instead of 60, dimension dooring 30 or 50 feet instead of 400+ feet, etc). Some abilities are more powerful (chilling tentacles vs. black tentacles) but are either higher level powers or have other restrictions (one mass of tentacles at a time).
I partly agree with you except that I do see the fact that the Warlock invocations "time reliant ones" like fly and invisibility are 24h duration which makes them a bit more powerful in that sense.