Is spell dmg worth at high levels?

[MaxWilson]

Correct!

Eldritch Blast does not require you to see the target, and since they can't see you, neither side has Advantage or Disadvantage. You can therefore simply pinball them about with Repelling Blast, getting lots of damage off of hazards (like Wall of Fire, Create Bonfire, oil, etc) and repositioning them for ideal AoEs (like Synaptic Static, NOT hitting your allies!).

As an aside, the usefulness of Repelling Blast is also why it's so easy to get multi-hits on Maddening Hex, despite its modest AoE size (though Yam doesn't take that Invocation, it's a resource-efficient damage tool for many Warlocks).

Huh. You're right, it doesn't. Apparently at some point I got myself mixed up on that. This means that True Seeing/See Invisibility is far less important for warlocks than I had believed, and one of what I thought were the core scenarios for Fighters over Warlocks just doesn't exist. Interesting, and my bad.

Nice point about Repelling Blast + Maddening Hex.