With Recover, Eviolite P2 will always beat Magnezone (without Charge Beam) unless you get some fairly ridiculous crit hax or paralyze hax or Flash Cannon Sp Def drops. Magnezone shouldn't be a consideration if you're just thinking about HP Water. Sally would very much like an ice resisting partner. So initial thought would be Heatran or Suicune. I'm more inclined towards Suicune partially because I've had more success with that, but it's also just better for your team I think. P2 can take care of most electric types (It's awesome how most of the hard hitting electric types have lighting rod / volt absorb / motor drive that Porygon2 can just switch in and wall to death... of course too bad Magnezone isn't one of those). And obviously Salamence can switch into grass moves fine. On the other hand, Sally's Intimidate will allow Suicune to set up a lot easier (I'm assuming Bold Calm Mind with Rest of course). So there is a fairly good synergy between all 3. Heatran has good synergy too... Not sure what set you'd be using. Every Heatran set I've used before have been at most just decent though... Anyway good luck.