My bad, I knew I was forgetting something but I couldn't put my finger on what.
Anyway, Solar Power is indeed residing in the priority 2 bracket, and while I was at it I took the occasion and grabbed my 2 DS to test the very last group (the 28 bracket) since there is no way to test it correctly in-game, and found out that :
_ "Pokémon is switched in" is still 28.0 but alone (didn't expect that, this caught me off guard);
_ Lunar Dance and Healing Wish group is really 29.0;
_ Entry hazards group is really 29.1.
I edited my previous post to correct those mistakes.