The change to Signum Crucis to make it do aoe damage is a really neat idea for making acolyte leveling more interesting. The issue is the range of it is so small that it is hard to get off reliably without face tanking the mobs, and if you are face tanking the mobs then you get interrupted quite easily. Also, acolytes aren't exactly tanky so its quite a risky skill to use at the moment versus just healbombing mobs.
With this in mind I would like to suggest some possible tweaks to the current version of the skill that would hopefully make it more viable:
1. Make the skill uninterruptible.
2. Make the skill aoe bigger.
3. Make the skill castable on a player clicked location rather than around the acolyte's fragile body.