Nice, I had created a thread just like this a few moments ago 
I defeated them on the second try when I was training my Electivire from scratch, so he was a non-usable pokemon (as he was level 30).
My party was all level 67, except Dragonite who was at 70. Didn't use any potion, as I mainly OHKO most of the pokemon, even Spiritomb, with Dragonite's Outrage doing a critical on him.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
