hmmm, idk why people are complaining about the consistency of this card: I mean, of course it needs to have a high attack cost -- it desperately needs to be balanced, otherwise we would get a new seismitoad on the format -- and nobody wants that, right? =/ And I will discuss how that can be:
First, from the comments that I read, I don't really see much problem with Ampharos:
1. Safeguard and Ampharos' second attack: of course safeguard pokémon are rotating out, but beautifly has a similar ability to safeguarders and its ability can't be shut off by silent lab =P Besides, we still don't know everything about the other cards that will be available, like that Giratina EX that probably has an ability that prevents damage from something (EX's? basics? mons with tools? maybe megas... who knows?). I can't see this EX being played exclusively for the effect of the second attack, but at least it is there (for instance, I don't remember any attack that ignores effects coming from any lightning mon at the current format =/).
2. Toad: Toad is currently being shut off one card at a time: first with LTC's ban, then a bunch of annoying stuff rotating out in a few months (virbank and lasers), and the addition of so many new grass type cards, and support for them. In other words, I think it wouldn't hurt to put one or two megaturbos in an Ampharos deck =P
3. And, btw, remember that 4 energy cost for an attack that has 2 colorless on it is not too much to ask: you can power it up faster using DCE, on the worst case =P
And, for the discussion I promised, I would say I believe this card is kind of OP: imagine combining it with vileplume! I mean you can shut off item cards and get your opponent's active pokemon paralyzed, which means it CANNOT retreat (at least I can't remember any card that is not an item that allows you to switch the active mon -- remember that keldeo is rotating as well). Of course your opponent can use something like AZ to scoop up the active mon, but that will obligate your opponent to discard any energies and tools attached to his/her active mon, and also burn his/her supporter for the turn with AZ =P Decks that focus on donphan (oops, rotating out soon =P) and Gengar EX could try to prevent this lock, but there is a maximum number of AZ's and robo subs (and remember that vileplume blocks it too) that can be played since LTC will soon be banned =( -- and, (surprise, surprise) Gengar is only one lysander away since 170 gets rid of it in one hit =O
Now, combine MAmpharos with rough seas, and realize that you have a 220 pokemon that kills or paralyzes your opponent's active every turn, and can heal the damage for free at the beginning of your next turn; a vileplume on your bench could prevent your opponent to switch his/her active mon, and basically the only way to break this lock would be lysandering out the vileplume, which you would have to do very early before being crashed by this unforgivable mega =3
Oh, and for those that don't believe vileplume is viable, look again at that stadium that basically gives Caterpie's ability to every grass type in the game (and will come with this set).
PS: Also, that new special energy for lighting types removes M Ampharos weaknesses, remember? #FearThatFabulousHair XD