Floatzel is best used as a utility with the Kristy set (Bulk Up/Taunt/Baton Pass/Waterfall), and is not sturdy enough to use Rain Dance. Quick Swift Swim might seem attractive, but Floatzel usually won't survive to set up. 55/50 defenses is bad.
As usual, Bronzong is the best Rain Dance starter IMO, for a Taunting/Statusing/U-turning one you might want to try Crobat. Kingdra can also set up Rain Dance and sweep easily, although its defenses are around average, and MixDra almost always runs a -Def/SpDef nature.
A Rain Dance team with no Kingdra? =(
Anyways, Kingdra is a fast, mixed sweeper in the rain, Waterfall for Bliss and DM/Surf for anything else.
Thunder is not a viable option as there is a chance of not setting up the Rain, and it will have low accuracy in Sandstorm, especially if your Rain Dancers are down.
(It's still considerable though, seeing as the team will get major benefits from Thunder over Thunderbolt.)
You may want to try Persian as a lead if setting up Rain Dance is not a heavy priority.
(At this point, Persian is unable to do the NP/Hypnosis combo, and if you remove one of the attacking moves, then it loses sweeping power, so I have to say meh on that.)
CBMachamp may seem great with base 130 attack, but the set you're using is just a bad CBHera. Machamp wants No Guard Dynamicpunch.
(That's what I thought, but it's on the contrary. It can't be crippled by Will-O-Wisp, adding to its already gigantic attack, and paralysis is no longer a problem since it's already decently slow. Close Combat 2hkos Skarm here, which is what the speed EVs are for.)
Without Evs in Defence, Milotic is very vulnerable to strong physical moves. Surviving all sorts of boosted Thunderbolts does not outweigh the threat physical sweepers pose to you. Basically Heracross/Machamp can come in on Milotic and do a lot of damage.
Pretty big Heracross weakness. Magnezone and Mesprit are outsped by most Heras leading to an easy kill with Close Combat/Megahorn. ScarfHera is even scarier, outrunning Floatzel (without Swift Swim) and everything else, and you don't have a safe switchin on it.
Floatzel only needs 16 speed EVs to outrun almost all the threats in the metagame, but I reiterate - Floatzel is too frail to effectively set up Rain Dance.
I also don't see any of your pokemon (sans Floatzel and Persian) which can use Rain Dance to their advantage. So, if Floatzel is down, not much can benefit from Rain Dance, making it to be a waste of a moveslot somewhat.
Magnezone WANTS HP Ice. The only things that you would use HP Ground on are enemy Magnezone (Magnet Rise?), Heatran (Its faster than Magnezone). HP Grass is for Swampert which your team can handle well with Mesprit and Machamp.
Rain Dance teams are not aimed at reducing or nullifying Fire weaknesses, they are for the weather and its beneficial effects, Water moves x1.5, Swift Swim mostly. Therefore I see no point in including a stally Grass type or Forretress to stall in the measly 5/8 turns of Rain Dance.
Lack of walling is the major flaw in this team, allowing strong sweepers to wreak havoc on it. Basically if a Heracross or something else comes in, you will almost always have to sacrifice.
Conclusion: Needs more Kingdra
*image removed*? =(
