If you really need another member, maybe you could go for Zoroark, it massacred his entire team for me :3
But your team should be able to handle Radomus.
For me it was Serra because I would have so much bad luck with freeze hax and missing.
I had to get the Vulpix for the Drought so I could actually hit her Pokemon and make Blizzard miss.
I destroyed Florinia actually because I had a Charmeleon with Dragon Rage and Golbat which made Cradily really easy to defeat.