I am thinking about creating a magic sorc for Morrowind. Looks like I will have to use a heavy attack build for substain. What should be a decent baseline for the DPS Dummy Test for a Heavy Attack build? 15k-20k a good target goal to start out?
Heavy attack build? I'm not sure there's such an approach.
You can use CPs to increase the damage of your heavy attacks, and you can spend to increase the magic returned from them. In update 14 it's possible that people will invest in these a lot more due to various changes.
But aside from these specialty CPs, the damage your heavies put out scales off your max magic, the damage rating of the weapon, buffs, etc. What makes your heavies hit harder will make all of your abilities and heals better. So a heavy attack approach would be consistent with any decent dps build. I'm not sure if this was what you're asking, or if there was another question in there.