So recently I've run into an issue with some of my players concerning the tactical efficiency of the bad-guy spellcasters.
Specifically, we're playing a Pathfinder Adventure Path at mid-levels (they're level 10 at the moment), and we've butt heads a few times over how intelligent and prepared an enemy caster should be. One of their new favorite methods of exploration is running around always invisible (they bought wands and the Alchemist regularly makes potions of it), but when something does succeed at a Perception to notice them, they get upset when an enemy Wizard casts See Invisibility when told "intruders are here, and they make noise, but we can't see them". Or when the BBEG Wizard has Alarm cast on his entryway. In the past, I've had BBEGs previously use similar tactics (and was likely the source of inspiration for their behavior), but they vehemently complained when the baddies would cast invisibility before chugging some cure potions.
Now, for a 16+ INT spellcaster (the pinnacle of human intellect, for the real-life analog), these tactics seem completely fine to me, as anything I can quickly surmise on the spot, certainly these baddies who are smarter than I would be stat'ed and live in this world would be, no? I'm not altering their gear, merely playing them intelligently. They use their meta-knowledge (sometimes only subconsciously , thankfully) to devise tactics for future encounters, and the enemy spellcasters I try to ensure are only taking fundamental precautions in such a world (not quite Tippyverse levels, but basic things, like mages having Mage Armor ready to cast). As far as preparedness, I tend to keep the baddies a little less prepared than I would be if I was playing the cast.
Are my players being babies? Am I being too tactically ruthless? Where is the best place to draw this line? Should I only use tactics they've already broken the seal on? Obviously these are going to have subjective answers, but I'm looking for common lines in the sand or popular blog posts on the issue, if possible.