Unfortunately, if you wanted to level up a demon-summoning mastermind, you'll have to wait just a little bit, as that powerset will go live with Issue 17. And the expansion itself still isn't set to release until July, when a whole new slew of options will open up. But if you're a longtime City of Heroes player or a recent convert, there's a whole lot of things out there to shoot and one little assault rifle likely isn't going to do the job. Go ahead and get your pre-order in, and take a look at the improved website for the expansion while you're at it.
[ Thanks to Skystreak and Celestial Lord for the tip! ]