Ah. I think the issue there is that the damage of the explosion is based on the damage of the triggering attack. Golden Gun, Hammer of Sol, and even the Energy Drain strike all have much higher base damage than Scorch. The Scorch hit, sans burn, actually deals the same damage as the uncharged melee. I've made numerous posts, myself, suggesting that Brimstone should increase the damage dealt by Scorch. That would make it easier to actually get the kill needed to trigger the explosion, make the explosion more potent, and make Sunburst a little more appealing as a synergizing talent.