An oversight; not sure yet if I'll fix this to be closer to PnP or keep it to make Eldritch Blast more powerful.
I think I'd recommend keeping it metamagickable. Right now, it feels like Warlocks need a bit more "oomph" to their damage for later game content. Sure, you can cheese certain things by layering your spells but that requires tons of buildup. With empowered, their damage is comparable to a basic orb spell cast by a wizard or sorcerer.
I tested on trying to solo content on the test server, like Cursts, and its certainly possible, but it is a slog. A wizard, sorcerer, or a mechanically apt warmage are able to solo things already in half the time. Though, if you don't want to take soloing as a measurement of class strength (understandably), I've been considering how they would fit into a dungeon. For most lower tier dungeons, they're going to be auxillary damage. They are there, but they aren't really doing much to help. Until they get Ennerving Shadows, they might even cause some issues with how the AI likes to run at people who are casting spells. For mid-tier content, they are going to be good at hitting things with Eldritch Chain and softening enemies up. Higher content, however, is where they are going to struggle. A lot of enemies will just dodge their touch attacks. Their DCs will be pretty solid for Charisma-focused Warlocks and spells like Eldritch Doom will have mild use against foes like Salt Shadows and Ebon Knight Harbingers, but it will likely be doing 15-52 damage on a save or fail. Against enemies like the Sleeping King and Malthor, however, I feel they are going to be totally useless because their saves and AC are tough to overcome.
One thing that got brought up back during the Warmage release was the idea of adding a Weapon Focus: Touch Attacks, and possible Improved Critical: Touch Attacks. I feel like if any class really, really needs something like that, it's going to be Warlock.