Clefable IS a funny tech against water decks, but you're missing some things.
The big problem is energy attachers. I mean, DRE and Scramble Energy can help in this regard, but it's not quite enough to ensure you have either Clefable or Magmortar ready to go. Typholosion however, can attach energy from discard to the bench. Sure, it won't speed the active up. That's not important. It's vital to have a way to recover from knockouts, and that's what Typholosion offers.
Cleffa, Smoochum, Charmeleon, and Charmander offer little, if anything to assist you in your goals of Clefable and Magmortar. A lot of room just opened itself up for something like Typholosion. Additonally, the Growlithe count should be greatly scaled back to either 1 or 2 copies.
You'll need more Magmortar. At least 3. Preferably 4. Magmortar count should equal Magmar count. However, Clefable's fine as a 2-2 line.
Following trainers should be converted into more useful versions:
Switch -> Warp Point (to move cessation crystal away from active position and open up opportunities for snipe via Magmortar. Yes, 3 is better then 2 and 1.)
Pokeball -> MasterBall/Great Ball (ensured search is better)
Team Galactic's Wager/Mars -> TV Reporter (You want straight draw and puts energy in discard. Good. You don't need disruption of the hand as much. I suppose you could keep 1 wager if you felt you had to)
Mr. Stone's Project -> Roseanne's Research (No reason to stick with Mr. Stones if you're playing Typholosion)
2 Professor Elm's Training Method -> Something. (You can go with more balls or draw power. But more supporters isn't the best idea)
4 Bebe's search -> Celio's Network. (No reason to play Bebe's, it just sets you back and you don't even play EX pokemon)
Some Fire Energy -> Scramble/Double Rainbow Energy (Convert as you like, just try them out and see how many you need)
Give those changes a try. Typholosion in particular should help give you bounce back ability, which is vital for Magmortar (a Magmortar rush can handle it's own early game, but needs a way to recover from shocking knockouts). Upping the counts of some cards and clipping redundancy (IE: extra Growlithe, non-assisting Charmanders) ought to help.
