edit It's fixed, I just thought acid blast did a d6 of damage on normal hits.
So, I crafted the first 2 tiers of my pally's green steel scimitar. I put on regular acid (no burst) and 20 % heal amp. Occasionally I would equip it before I had my 3rd tier and the acid effect worked fine. But last night I crafted the 3rd tier, it looks like only the acid blast works. Most attacks only have 1 number with an acid symbol (the others are criticals), and I have seen that number hit 1 so I know the 1d6 damage from both acid effects isn't clumped into 1 number for some reason. I'm pretty sure they are supposed to stack but I would like some confirmation.
http://img37.imageshack.us/img37/2429/gsscimi.png is a screenshot of the scimitar if it helps.