Fanaelialae
Legend
You keep bringing up corner cases, countering specific spells, as if that somehow shows that buffing which is generally a worse option somehow becomes good. Casting lots of buffs just makes things harder on the party, and I'm not talking about math for the players.
It's not a corner case. It's a response to the idea that Dispel/Disjunction should be used in every encounter. Which in fairness wasn't something you brought up, but it was the conversation you entered into.
If enemies can use debuffs every encounter, they can also use counter spells every encounter. I don't remember the exact details, but I'm fairly certain that Dispel could be used to counter any spell as it was being cast.
Admittedly, it might be superior for the DM to use one of those better spells you mentioned, but if the DM isn't trying to murder the party, countering might be a more even approach. I seem to recall that high level caster battles could easily become rocket tag, where whoever won initiative was likely to win.