I will go 6/10. 6/10 for me means it's a decent card worth playing.
I am not 100% on the metagame but isn't there a dearth of worthwhile fire types?
While Heat Boiler relies on the opponent to give a status condition, it may deter them from playing Hypnotoxic Laser until Heatran is in KO range with it. I know that's the best time to play Laser anyway, but I often have people playing it a turn or two earlier than that with Virbank. And it also seems to me that this card could get some longevity with max potions and still be able to attack each turn with a Chandelure and DCE. Might be tricky to stream DCE, but if you have it you have it. Having 0 to 10 damage on you is better than 160 etc. (If you're 10 away from being knocked out you'll have to max potion BEFORE Flare Navigate, of course, resulting in the 10.)
He can 2HKO just about anything (using its attacks in order). True for a lot of dudes, but when we say that it's not uncommon for us to just be talking about 180 damage cumulative. This is 200 total damage as you charge up to being able to use the second attack. Handy for say Darkrai with Eviolite. If you're doing the second attack twice, we're in the 240 range. Of course, all this relies on Plasma Energy. But that's the whole point of this set in a way. Plasma Energy.
One more thing...Rock Guard is fun on this guy.
If you're in a situation where he's charged up and isn't KO'd by a fresh pokemon they bring up, you have a retaliatory OHKO in the works. That concept alone almost make me want to give this a 7 but it's foolish to rely on Tools to win the game with Tool Scrapper being so common.