This really is an odd behavior for the rules. However I have yet to do a setup exactly like yours. I imagine that you could use an SQL script to change the order in which database pulls the description. For example when it looks for the description for the price rule to post to the page it is pulling it from the first rule in line. This would need to be changed in your stored procedures to reflect that if there is more then one assigned rule to read the description from the second one or even both.

I am pretty well versed in SQL however due to the sensitivity of it and experience levels I don't want to give you the exact script for fear that if it kills your database you'll come to kill me :) Ask Susanne in a nice email and I am sure she can point you in the correct direction of a script to accomplish this.