From my experience, the AI prefers to target the Pokémon they can KO (regardless if this means using a move that damages the AI's partner heavily, like Fire + Water AI, where the Water one uses Surf).For people who have done the bait Pokemon/spread move teammate strategy in doubles, have you noticed a certain threshold at which the opponents don't target the bait as often?
I have a level 46 Sneasel that is currently EVed to be one point faster than my Eruption user (Entei), and its defenses are low enough that the opponents do attack it the vast majority of the time (even with Water moves). However, there have been some times I've wished it could do some more damage on its own rather than providing support. It has minimum defensive IVs, so if I leveled it up from 46 to 50, its defensive stats would go from 106/57/66 to 115/62/72. Do you think leveling it up and/or evolving it to Weavile would change the list of things that target it instead of Entei?
I say ''prefers'' because the AI can be very unpredictable sometimes. I remember back in D/P Doubles that Rampardos went for Head Smash on my Dusknoir a few times while I led with Dusknoir + Lvl 1 Smeargle. There have also been situations where they went for the Super Effective STAB on my Ghost lead, while they could have ''knocked out'' Smeargle, using a different move. In your case, you will most likely get into situations were the AI would go for Rock Slide / Earthquake + a move targeting Entei, having the AI think that they would knock out Sneasle (But you have sash etc etc).
tl;dr the AI usually will try to knock out the weaker Pokémon if it's stats allow them to do so, but there are still situations where the AI can be unpredictable.