if nt Sharpedo, then definately that Rotom-Heat. Not really doing enough to benefit a Rain Dancing team. And why Salamence? Why not something that more benefits from being in the rain, like Swift Swim SpAtk Choice Specs Kingdra?? Absolute monster. Thats STAB, plus Rain power, plus Choice Specs Surf off a base 95 SpAtk. The base isnt extremely impressive, but the outcome is when you get close if not OHKO both your opponents pokes at once while your partner is unharmed using Protect (assuming this bc you seem fond of it, possibly paired with Sharpedo to get a free Speed Boost as well?) AND Kingdra can take hits quite well, boasting a weakness to NOTHING except other Dragons, which in the Rain it can easily outspeed and OHKO with STAB Dragon Pulse.
If you couldnt tell, Kingdra is my favorite dragon. lol