Personally, I don't consider Binder and the UA Vestige Warlock to have any sort of relationship other than the word "vestige" being used for both.
They're vastly different mechanical experiences with some overlap in narrative concepts, but nowhere close to the same overall concept.
Plenty of things can exist that are "modern" that were also experimented with earlier eras; they simply didn't become part of the mainstream definition.
B/X has a lot of contemporary respect precisely because it did something "modern" well before that practice became commonplace enough to be...
Realistically, day-to-day living should cause XP loss, proportional to the amount of total earned XP, representing the natural erosion of the edge life-or-death experiences give.
Training and practice can ameliorate this decline, but not arrest it.
In the context of "we're focusing on one big fight, not an attrition model", does a high level wizard having 5 5th level slots with 5 known spells for each big encounter work? I would say yes. Are there plenty of spells that would need to redesigned? Absolutely.
This seems like a change for...
I have done that, if they're really "crushable fodder" like kobolds. But I use these rules pretty often for 3-4 similar creatures, like a group of 4 ogres, more for pacing and ease of tracking than anything. It's easier for me track one pool of 200 HP than 4 different stacks of 50.
My house rule is slightly different (I think, I haven't read Draw Steel!) in that killing all the minions requires both a successful attack on each minion and the depletion of the entire communal pool.
My minion approach is to give them a pool of communal hit points. So 20 soldiers for an 11th level party might have 300 hit points (15 HP per soldier). Whenever an attack lowers the communal pool by 15, that soldier goes down. But it requires a successful attack to actually make the soldier...
It's pretty wild how this thread has gone from "Are the differences between 2 distinct 27 point buy arrays meaningful for balance" to "actually, using a d20 means nothing is ever balanced". That's more variance than a d100! :)