While this is actually a character skill bug there is not a category proper to it, being a crafting skills. This is a copy of a bug report i sent just to let everyone know the details of the issue. I did some rather heavy testing.
Issue: Medicinal Use (Alchemy Skill)
Bug will happen at any time any location.
Intended function (at 2 skill points invested) increases the duration of potions by 20%.
This is easily observed with health/magicka/stamina recovery potions and addons. Also the greater healing potions 14s duration is large enough to observe 20% duration with a stop watch.
A Lv.20 crafted base healing potion will heal 110 over 10s (11 health per 1 second ticks) the greater healing potion (In Alchemy using all 3 ingredients with health recovery) heals 154 over 14s (still 11 health per one second ticks).
With the above medicinal use should have increased the greater healing potion to 16.8s even assuming unfavorable rounding we should have 16s duration (assumable at 11 health per one second ticks) however there was still only 14 total heals of 11 for a total duration of 14s (the healing stayed the same per tick, the healing had the same number of ticks, and all healing ticks completed within 14s as per usage without Medicinal Use.)
The effects of Medicinal use (as per its name suggests) does not actually work for medicinal use. Which is largely what this bug report is for.
The second part is difficult to test with no ability to see active potion buff duration counters however there are graphical effects (for example cracked or barrier around the health bar for up/down armor) at first, using a stop watch the duration should have gone form 10s to 12s and I saw no apparent effect, however I decided to test again using the actual character sheet to find the buffs do in fact last 12s (but the graphic will only last 10s).
The second and minor bug report is the graphical effect not lasting for the extended duration.
Edited by gothickaiserub17_ESO on April 19, 2014 10:22PM