If there is anything Josh has done well in terms of gameplay design, it is to remove pre-buffing. It might make sense to pre-buff yourself from a narrative standpoint, but from a gameplay perspective it's just tedious busywork that adds nothing. It's muuuch better to actively think whether to buff or to use other things in combat.
If you are casting the same buff every encounter, or have it constantly up anyway, there's something wrong. Either the encounters are trashy, copy-pasted time-wasters, or pre-buffing exists but should be baked into the classes and not be an extra button to push after every rest. What I mean is that it's better to weigh the pros and cons of buffing, debuffing, damaging, healing etc. than the buffing layer being exclusively out of combat. It just makes more sense gameplay-wise.
I’d like to present some counterarguments vis a vis the removal of pre-buffing.
A lot of buffs are situational. You don’t always want to have them on. There are hard counters: they can be dispelled. You then have to reapply the buff or do something else. They have varying lengths. You can’t pre-cast every buff and expect it to last the whole fight let alone the whole dungeon. They take up spell slots! The most obvious one, they compete with other spells. For every Defensive Harmony you have one less Cure Serious Wounds. I’m not even going to get into sequencers/contingencies.
More specifically concerning your points:
It's muuuch better to actively think whether to buff or to use other things in combat.
Pre-buffing doesn’t negate that, you still have to make the decision mid combat whether to reapply a buff that run out/got dispelled, cast one for the first time or do something else, as well as having to make an additional choice before an encounter regarding the type or number of buffs to cast.
If you are casting the same buff every encounter, or have it constantly up anyway, there's something wrong.
Certainly, shit like Mass Cat's Grace etc do work in favour of your point, but that is the uninteresting spells’ fault, not inherent to pre-buffing.
or pre-buffing exists but should be baked into the classes and not be an extra button to push after every rest.
That would be straight removal of tactical choice, which is decline, and as I indicated pre-buffing does not equate to mindlessly casting things after resting.
What I mean is that it's better to weigh the pros and cons of buffing, debuffing, damaging, healing etc. than the buffing layer being exclusively out of combat
Having all of the tactical decisions be made during combat (apart from leveling/memorisation phase) constricts the design space for interesting spells. During combat actions that affect your opponents are the most apparently pressing and the time scale to make them is smaller; buffs that may be cool but are obviously a weaker choice get ignored.
Note I haven’t played Deadfire yet after I tried the backer beta and got triggered by the reduced party size and everything per encounter inanity. Still, concerning Sawyer’s choice of pre-buffing absence from PoE despite being a big part of IE games, I give it an adamant thumbs down.