Interestingly the results were the same for Spiritual Serenity, Quiescence and Stoicism with the potion - I didn't test Torpor and don't have BoT but it should have been the same for both. Now that the UI shows the buff duration it makes testing the HoTs much easier than in the old days!
Test one - SCRM + EE5
In theory: 4 * 1.50 * 1.15 = 6.9 ticks
In practice: 0:42 on the icon, 8 pulses of healing
Test two - SCRM + Zephyr of Brell
In theory: 4 * 1.50 * 1.20 = 7.2 ticks for Stoicism and Quiescence
In practice: 0:42 on the icon, 8 pulses of healing
Test three - SCRM + EE5 + RA5
In theory: 4 * 1.50 * 1.15 * 1.05 = 7.2 ticks
In practice: 0:48 on the icon, 9 pulses of healing
Test four - SCRM + Zephyr of Brell + RA5 for Stoicism and Quiescence
In theory: 4 * 1.50 * 1.20 * 1.05 = 7.56 ticks
In practice: 0:48 on the icon, 9 pulses of healing
(Picture taken during test three, using Talisman of Wunshi and Spiritual Channeling to full effect)
I was so astounded at getting an extra tick I tried it around ten times - and every time, even with just an EE5 item equipped I got an extra tick out of the HoTs.
So, to sum up - even though the maths doesn't suggust it, in my experience I was able to repeatedly get an extra tick out of my HoTs with a 15% extension item. I'd imagine most non-raiding shamans have either a 15% or 20% boost to their buffs, in which case they should benefit - I can't test 25% and 30% focus items though as I don't have any!
