So Light Arts definitely provides a bonus to both Regen potency as well as duration, I went and did some testing to see exactly how the bonus works. Turns out it's level dependent for both potency and duration. I updated Regen Spell category page and Light Arts page on BG Wiki with this testing for Regen spells. Here's the raw data, all with Light Arts (done on test server to manually modify level):
SCH Lv. 18: Regen - No duration bonus
SCH Lv. 35: Regen - +12 seconds, +6/tick
SCH Lv. 40: Regen II - +18 seconds, +9/tick
SCH Lv. 50: Regen II - +24 seconds
SCH Lv. 80: Regen II - +40 seconds, +19/tick
SCH Lv. 99: Regen - +48 seconds, +24/tick, Regen II - +48 seconds, +24/tick
Previously known:
The potency bonus is flat across all tiers of regen (tested with all Regen spells).
New stuff:
First, I think the duration bonus is a constant # of seconds, not a percentage, as Regen (I) has a greater base duration but seems to get the same duration bonus (in seconds). Second, the duration bonus is not # of ticks because the spell will end between ticks at certain levels. Third, I couldn't test potency because I had no easy way of dropping my HP at levels below 35 on the test server (was using sublimation to drop it), but there's definitely no bonus for at least duration at some level X and below. Level 18 gets no duration bonus for sure (Regen was exactly 75 seconds). If I had to guess, I'd say piecewise linear going from 0-18 seconds from 25 and 40 and then 18 to 48 between 40 and 99.
My theoretical equations for the bonus are (level-1)/4 rounded down for potency (I would have said level/4, but level 80 at 19/tick, for example, wouldn't fit). Double that number, in seconds, for duration seems to fit reasonably well. This doesn't fit the duration data perfectly, but it's close for a first pass.
There are some blanks I need to fill in to verify this info, but does this seem correct? Any other input?
Specifically interested in the following:
-How does the equation change below level 40 (and is it level 40 where the equation changes)?
-What's the minimum level that receives the bonus (and is that minimum different for duration and potency)?
-More info for duration bonus?