In RMI, Directed Spell was limited to 10 ranks, for a +50 bonus max.
RM2 changed that, allowing the skill to be developed normally.
+3 per level for prof bonus is +60 at level 20, then can progress at +2 per level till level 40, then +1 per level till level 60. This option is listed on a table in Lords of Middle Earth Volume I.
If you dislike the+1/2 (which is a +1 with two ranks purchased) after 30 ranks, simply make it +1 after 20 ranks.
There is also an option in one of the companions to make all OB skill progressions 5/4/3/2/1. The result is big numbers to play with.
When in Rome, tell em to go &*&^ themselves and do it your way.