You have a really valid point here that I did not think about. If the design team was to remove the self-target + no Accession restriction on RDM gain spells it would allow him/her a lot more options on how to buff a group vs. a WHM's Boost-spells. Overall, RDM gains a unique feature with out becoming a lesser version of a WHM.
I don't think a magic debuff series would be possible because of how strong a high tier Shell is. But if it was a low % like -5% with a decent Enfeebling skill gear set it might be possible. I'm still not sure how I feel about this one.
I see a magic evasion debuff as being fully possible and a really note worthy spell for RDM. I know DNC has stutter step but it seems very odd that DNC is the only job that can do this (I have no idea if BLU can so if I'm wrong please correct me), when RDM is designed to debuff. I think this spell would increase RDM's invite rate a lot since a RDM would not have to keep stacking it like a DNC.
As for a 3TP/tic Regain.... We can always dream. lol. This would be like refresh was during the 75 cap era. Let the spell stay off a melee for 2 seconds and they start to rage that you're not doing your job. lol