Well after watching some Wi-Fi battles using a pesky tangela, I think it's worth training. Using the eviolite and pumping up its HP, Def, and Sp. Def EVs, it can be a great stall Pokemon.
Mine knows
- Leech Seed
- Sleep Powder
- Toxic
- Protect
Impish Nature
He can't stay in the whole time, though, so make sure you have a good team that could back him up.