The purpose of Phoenix Dive needs to be examined; it serves as a means of quickly escaping a bad situation or inserting a fighter deep into enemy lines. One only has to ask: do either of these scenarios sound like a moment where wounding yourself sounds like a bright idea?
If you're in danger and need to escape, is adding burning damage to your list of troubles really the best of decisions?
If you're going to insert yourself behind enemy lines with little to no support, is damaging yourself upon arrival really the type of plan you should be running with?
When it comes down to it, the ability is little more than a Warrior's leap or stomp as seen in other games, except with the additional silly idea of torching yourself in the process. It's like someone said
"how can we make a Warrior's leap/stomp cooler than it already is? I know.. douse yourself in oil and light a match first.. yeah!".
