The Cleansing Burst overcharge of the Engineer’s Healing Turret does not contribute to the Condition Remover achievement. Here’s a video to show it; I feel I must apologize for the low quality of the video, but you can tell that A ) the Poison condition I am afflicted with during each segment has much longer to last than it does, and B ) that the number next to Condition Remover does not change (in fact, it stays at 15%; I cured three stacks of Poison with Elixir C just before the videos were taken).