D&D 5E Undead Sorlock Advice

[Flamestrike]

multiclassing never is a great bargain as a caster. But at level 9 you get most out of your aberrant mind so... if ever, it's then.

You're delaying 9th, 8th, 7th and 6th level spells.

It only makes sense if you regularly find yourself having to fall back to cantrips (or use them regularly) - i.e. if your DM bothers to police the adventuring day in any way shape or form.

With a DM that doesnt, and you only get 1-3 encounters per AD, it's not worth it.

 

[WASDHammer]

Without asking for spoilers, I think my concerns that initial caused me to consider MCing into Warlock twofold

1) To just the "safety" of a free/low resource damage spell for when I run out of spells (or conversely, allowing me to more aggressively use my spells without fear of being rendered useless if they run out)

but also 2) As an Aberrant Mind, many of my spells are Charm related (at least those that maximize the traits of the subclass), and I think I'm finding myself running into a lot of NPCs in Strahd that resist charm effects. Now you could certainly say that I could/should have selected a better subclass from the start, but I do really like my PCs story arc with AM Sorc., but the MCing would then give me some straight damage to supplement my control-based spells.

 

[Paul Farquhar]

AB gets to swap out two spells when they level up. You could always pick up a bit of pyrokinesis.

For example, Silvery Barbs could be a psionic spell. This could replace Shield from the general list, freeing up a slot for Fireball.

 

[UngeheuerLich]

You're delaying 9th, 8th, 7th and 6th level spells.

It only makes sense if you regularly find yourself having to fall back to cantrips (or use them regularly) - i.e. if your DM bothers to police the adventuring day in any way shape or form.

With a DM that doesnt, and you only get 1-3 encounters per AD, it's not worth it.

And this is ok as a play choice. If that fits the character you can do worse. You keep up in at will damage an utility and gain a bit of extra sustain with 2 first level spells per short rest.
Not every character has to be compared to a full caster. Being 2 spell levels behind is still way ahead of an artificer or paladin.
It is a very one sided view on the game to only look at the highest spell level.

 

[UngeheuerLich]

Without asking for spoilers, I think my concerns that initial caused me to consider MCing into Warlock twofold

1) To just the "safety" of a free/low resource damage spell for when I run out of spells (or conversely, allowing me to more aggressively use my spells without fear of being rendered useless if they run out)

but also 2) As an Aberrant Mind, many of my spells are Charm related (at least those that maximize the traits of the subclass), and I think I'm finding myself running into a lot of NPCs in Strahd that resist charm effects. Now you could certainly say that I could/should have selected a better subclass from the start, but I do really like my PCs story arc with AM Sorc., but the MCing would then give me some straight damage to supplement my control-based spells.

A reasonable choice. If you can actually work it into the story when you gain your first level of warlock, that would even be a bigger plus. Even if you go from sorc 8 to sorc 7/ warlock 1.
I think the curse of strahd campaign is perfectly suited for such a switch.

 

[WASDHammer]

I think that's the thing that excites me the most. It works quite well with my current story arc. If anything, that was the reason I decided to do it in the first place, but didn't want to make myself a weak PC just for the sake of story. But it sounds like that would not be the case.