1) I dismiss the Cyclops and Xavier conversation in the same book because there is a TON of other canon out there that refutes what they said. For the sake of this issue, Storm's powers worked exactly how Xavier said it did. However, that is not the case for all Storm stories and other writers have had a different take on her powers. I don't sit around and just call things PIS randomly because I don't like it. When I call something PIS, its because there are other stories that show Storm to be stronger than what said issue has claimed.
2) Regarding the Blaze thing, she is every bit as powerful as she claimed to be. Notice how the team was fearful of her being able to toss another blast. This is not some empty boast about her power. Furthermore, the issue stated that Sienna's powers were, "
...similar in effect, if not in origins to the power of the Phoenix!" as revealed in the scan below:
http://2.bp.blogspot.com/-dNEMCTh2Tw...c42/RCO014.jpg
Also, if you read the panel where she talks about how powerful she is, she is speaking very casually and very sanely:
http://2.bp.blogspot.com/-r_zATjnVV1...c42/RCO038.jpg
http://2.bp.blogspot.com/-n9w6z_1eeR...c42/RCO039.jpg
In her very next appearance, Excalibur issue 73, she attempts to kill Nightcrawler by CASUALLY throwing a blast powerful enough to fry Kurt to a crisp with enough power left over
to sink Muir Island and half of Scotland Mainland:
http://2.bp.blogspot.com/Y5P10_XkcCy...ov9HFslY=s1600
She casually tossed off this blast, in other words, she didn't exert any strain whatsoever to throw a blast this powerful at NC and her only aim was to kill him. So, this blast was nowhere near her full power...which it wouldn't be seeing as how she is strong enough to split the planet like a ripe melon.
3) Sienna has far more raw power than Magneto. He isn't even on the map where her power is concerned. Trying to limit Sienna Blaze by trying to prop up Magneto is silly. The lady is exactly as powerful as she claims to be. Its obvious from everything the issue stated and her following appearance in Excalibur that she's not bragging about her power levels, rather Blaze is just telling it like it is about how powerful she is in a matter-of-fact way.