Your main offensive ability will be previously mentioned Solar Barrage. Use it on an enemy, to deal some serious damage and magnify the power of the next attack (or an ability) on that same enemy (and nearby foes). Remember, that after using Solar Barrage, you should follow up with your strongest attack (your ultimate, Nova, for instance) to maximize the effect.
Before you begin your assault with your Solar Barrage (and a following attack), use your Backlash. This skill causes the enemy to accumulate received damage for a few seconds. After the effect ends, the enemy gets the stored damage, increased by a percentage value (and with a Purifying Light morph it also heals nearby allies). If you use your abilities in the right order (Backlash -> Solar Barrage - > some powerful attack), there's almost no chance that any enemy hit will survive that. Obviously, more powerful enemies (and bosses) will have no trouble getting through your combo, but it still will chunk a serious amount of their health. All you have to do is rinse and repeat, until there's no one left.
Besides those skills, don't forget to use your Sun Fire and Binding Light, which, besides the obvious damage part, offer some nifty amount of crowd control. The former will allow you to Snare your enemies, decreasing their movement speed, and the latter causes the enemies to have a 50% chance to miss their attacks - and knock them off balance if they do so.
Use the second (or the first one, if you haven't swapped anything but one skill) skill set in emergency situations - whenever your healer can't handle the situation (or is dead on the ground), when you are cut off from the rest of your teammates and your healer can't save you, or when there's simply a higher demand for healing and supporting. Similar to playing as a healer, try to lose your tail whenever the enemies start chasing you and allow your teammates to take the aggro - it will allow you to spam your skills from afar without much effort.