I loved that issue, too, and really like Siena Blaze a lot. Partially because she was a boss in a Sega Game Gear game I had when I was a kid and she hurled tornadoes at you.
I do agree Siena needs to have her powers tweaked. Keep the devastation, but take away the chance to destroy the earth, or at least make her sanity not so... unpredictable.
The writers are free to use Siena at any time, though, with her being resurrected during Necrosha. Although I'll never understand why the whole Neverland concentration camp storyline wasn't more controversial at the time, or even now.