Why do monsters attack certain targets?

[Crystalion]

I've noticed on Meph runs (sorc with natures peace) using oak sage , Meph will 9 times out of 10 target the Oak , whether the oak is in front/Level with me or behind me , it gets hit by mephs lightning and goes down immediately . Just an observation .

Because of Meph's local terrain I tend to think of him as a "pushover" among act bosses. Nonetheless, what you point out here raises an interesting opportunity with Iron Golems and Shadow Warriors, who can both be immune to elemental and positioned to take ranged attacks from Meph ad nauseum. (alas this isn't terribly important trivia, as you can already sleaze Meph at range without him casting a ranged attacks in return).

Of course, perhaps some of Meph's attacks (ranged) have a physical component, in which case the IG would get trashed (but the SW could be trivially recast, as long as you kept Fade up yourself, so the SW would quickly cast it for immunity).