You're pretty much correct. The Phantasy was a big deal back in the day, but it really hasn't been a mainstay venue like the Grog or Peabody's has been in the past couple of years. In fact, I hadn't been to the Phatasy in at least a decade until last Sunday. That's why the timing of this was so odd - it was almost as if the metal gods were telling me and my brother to go there one more time before it was gone (although that seems not to be the case now).
Anyway, there is also the Agora for larger shows. It is similar to the Phantasy, but bigger. Ministry and Meshuggah played there in 2008. Also, we have a House of Blues, which hosts metal shows from time to time. I've seen Behemoth there before (also in 2008, when they toured with Gojira and company). Clutch played there a few years ago, too. On an even bigger scale, there is also the Wolstein Center at CSU (where I have seen Tool, Isis and others) and of course Quicken Loans Arena (where Metallica is playing with Lame of God in October).
Last but not least, Cleveland has a couple of outdoor venues such as the Time Warner Cable Amphitheater and Nautica Stage in the flats (where shows such as Gigantour have taken place), and Blossom Music Center in nearby Richfield (the site of the Mayhem Festival in two weeks) to round out the possibilities for metal shows.
So as far as venues go, we are blessed. Now all we need are some consistently decent crowds to draw the freakin' artists in. This is becoming a big problem for me, because I go to shows and am psyched to be there, but it seems like the attendance / crowd reaction from other folks is sometimes sorely lacking. Isis got a good reception a few weeks ago at the Grog, and of course you know the crowd at Carcass (at Peabody's) was awesome, but last year's Made Out of Babies show at the Grog only had maybe thirty people in the audience. The crowds can be really spotty that way - that bugs me a little, because I don't want to see artists stop including Cleveland on their tours. The merch guy for Necrophagist told me last Sunday that "It looks like Drew Carey was wrong - Cleveland doesn't rock." I hate hearing stuff like that.