Basic stats page (v2.2.12) is showing
Int 1008
Spirit 817
MP5 531: Mouseover shows 772 O5SR.
Gaining 772-531 = 241 when going O5SR implies 2*241=482 Spirit regen (factor of two because Intensity already gives me 50% spirit regen).
I believe the formula for spirit regen is 5*(.001+sqrt(int)*spirit*.003345) = 434.
So I'm seeing a discrepancy of about 10% on O5SR regen?
HT Heal: Shows 12229 (SP is 2644). I think that would be consistent with ET being multiplicative, but http://elitistjerks.com/f73/t37038-restoration_glyphs/p8/#post1240879 showed ET as adding .4 to the HT coefficient, not multiplying by 1.4.
Nourish: I don't have test numbers for these (I'll try to get them):
1) I'd assume that if ET is additive for HT, it would also be additive for Nourish. Rawr is using multiplicative.
2) I think I've heard the Glyph of Nourish bonus (and the tier bonus) are both multiplicative, so with three HoTs and both bonuses you'd have xxx*1.18*1.15. Rawr has these as additive.
3) I'd assumed that the 20% bonus for having any HoT present was multiplicative. Rawr has it additive with GoN. I don't recall any seeing any tests one way or the other.