I really like this set. In my humble opnion, Insomnia is a much better answer to Sleep Powder than a lot of these Rest Talk sets because you aren't leaving your success up to chance. My only issue with it is that Magby is usually OHKO'd by Ancient Power after rocks.Magby @ Berry Juice
Ability: Vital Spirit
Level: 5
EVs: 236 HP / 116 SpA / 156 SpD / 36 Spe
Modest Nature
- Flamethrower
- Psychic
- Hidden Power Grass/Fighting
- Will-O-Wisp/Toxic
200+ SpA Life Orb Tangela AncientPower vs. 236 HP / 156 SpD (custom): 16-21 (66.66 - 87.5%) -- 81.25% chance to OHKO after Stealth Rock
If rocks are up, Magby can come in safely on HP Fire and Solar Beam. Those attacks will put Magby at 50% or lower, so it can heal back to full with Berry Juice, survive Ancient Power the next turn, and KO Tangela with Flamethrower. It can't come it on Ancient Power, and if it comes in on Sleep Powder, it'll (usually) be KO'd by Ancient Power the next turn.
If there are no rocks, it can come in safely on anything except HP Fire for the reasons you stated. For the most part, this set works pretty well against Tangela, nice job!