Politoed hasn't gained much at all in Gen 6. Drizzle only lasts 5 turns. However, Politoed can still have playability. Yes, of course, he can be used in tandem with a Kingdra if you want to, but there's actually more than meets the eye here.
What Politoed is, now, is just a simple pokemon with an ability that boosts his water STAB by x1.5. That's pretty significant for a pokemon with base 90 SpA. Surf did get nerfed, but 252 Modest Life Orb does 43.31% - 51.48% to Maxed Specially Bulky Jirachi (a baseline pokemon with 100/100/100 defenses). Specs Hydro Pump does 61.13% - 72.27%
Jirachi is bulky as hell to begin with and has/had uncommon SpD spread, so you'll probably be doing quite a bit more to many other switch-ins. Speaking of bulk, Politoed has his own 90/75/100 defenses to work with.
Politoed's teammates such as Rotomw-W, Ludicolo, and Kingdra can also quite logically use HP Fire now. It DOES nerf your speed IV down to 30, but you can also get around Ferrothorn better, and it's also nice to have for Scizor and Genesect.
Finally, politoed can use rest/sleeptalk/scald/xxxxx for much better staying power this time around. After using rest you are semi-disabled for only 2 turns and you can come back for more later.
Rain seems to be a perfectly balanced play style now. You can switch politoed in, switch it out, and you have 4 turns to swift swim. Some people might think that rain is too weak now, but remember that we are seemingly moving into an era of bulky offense rather than speed demon hyper offensive teams. It will take some evolution on your part to make a rain team work.
Remember this. Politoed needs to be switched in much more repeatedly and you also need to switch to your sweepers as fast as you can before the rain runs out. There is compensation for this. You are free to use Kingdra, Kabutobs, Omastar, Ludicolo, Poliwrath (Attack increased from 85 to 95), Seismitoad (Attack increase from 90 to 100), Manaphy, Thundurus, and Tornadus-T. You should either go very bulky so that all the switching you do is manageable, or you should go very powerful and wallbreaking, so the match does not last long enough for the switching to count against you. Make sure everything has functions outside the rain.
Here's a set to try:
Politoed @ Leftovers
Modest
124 HP, 232 SpA, 152 SpD
-Rest
-Sleep Talk
-Scald
-Psychic
With the HP EVs you end up at 352 HP which is a nice Leftovers number. The SpD EVs make it such that MegaGengar only does 39.2% - 46.3%. After rocks and leftovers it's a 3hko. You stand a decent chance if he tries to trap you (even if you're asleep), but crits and defense drops would ruin you. The rest is dumped into SpA for obvious reasons. Rest gives you crucial staying power and you can start trying to wake up when you're against pokemon like skarmory, jellicent, chansey, blissey, forretress, and other such defensive mons. Do not let anything start boosting on you.
What Politoed is, now, is just a simple pokemon with an ability that boosts his water STAB by x1.5. That's pretty significant for a pokemon with base 90 SpA. Surf did get nerfed, but 252 Modest Life Orb does 43.31% - 51.48% to Maxed Specially Bulky Jirachi (a baseline pokemon with 100/100/100 defenses). Specs Hydro Pump does 61.13% - 72.27%
Jirachi is bulky as hell to begin with and has/had uncommon SpD spread, so you'll probably be doing quite a bit more to many other switch-ins. Speaking of bulk, Politoed has his own 90/75/100 defenses to work with.
Politoed's teammates such as Rotomw-W, Ludicolo, and Kingdra can also quite logically use HP Fire now. It DOES nerf your speed IV down to 30, but you can also get around Ferrothorn better, and it's also nice to have for Scizor and Genesect.
Finally, politoed can use rest/sleeptalk/scald/xxxxx for much better staying power this time around. After using rest you are semi-disabled for only 2 turns and you can come back for more later.
Rain seems to be a perfectly balanced play style now. You can switch politoed in, switch it out, and you have 4 turns to swift swim. Some people might think that rain is too weak now, but remember that we are seemingly moving into an era of bulky offense rather than speed demon hyper offensive teams. It will take some evolution on your part to make a rain team work.
Remember this. Politoed needs to be switched in much more repeatedly and you also need to switch to your sweepers as fast as you can before the rain runs out. There is compensation for this. You are free to use Kingdra, Kabutobs, Omastar, Ludicolo, Poliwrath (Attack increased from 85 to 95), Seismitoad (Attack increase from 90 to 100), Manaphy, Thundurus, and Tornadus-T. You should either go very bulky so that all the switching you do is manageable, or you should go very powerful and wallbreaking, so the match does not last long enough for the switching to count against you. Make sure everything has functions outside the rain.
Here's a set to try:
Politoed @ Leftovers
Modest
124 HP, 232 SpA, 152 SpD
-Rest
-Sleep Talk
-Scald
-Psychic
With the HP EVs you end up at 352 HP which is a nice Leftovers number. The SpD EVs make it such that MegaGengar only does 39.2% - 46.3%. After rocks and leftovers it's a 3hko. You stand a decent chance if he tries to trap you (even if you're asleep), but crits and defense drops would ruin you. The rest is dumped into SpA for obvious reasons. Rest gives you crucial staying power and you can start trying to wake up when you're against pokemon like skarmory, jellicent, chansey, blissey, forretress, and other such defensive mons. Do not let anything start boosting on you.