DoT Extension degradation

[Noobieguy]

I was looking at the Detrimental Extension of:
HoT raid focus (Increase spell duration by 35% up to level 90, lose 5% per level over cap)
versus VoA group T3 ear (Increase spell duration by 26% up to level 95) and was wondering about the math of how much it degrades over level cap.
I am unsure and wanted to ask you guys if this is correct, or if I royally messed it up and need major clarification / educating on this.

This was what I came up with for the HoT raid ear:
Level 91- 35% (.95)= 33.25
Level 92- 35% (.90)= 31.5
Level 93- 35% (.85)= 29.75
Level 94- 35% (.80)= 28
Level 95- 35% (.75)= 26.25

SO if this is true, group VoA Det. Duration focus won't improve any HoT raid focus (this is the Tick Tock ear I am wearing). Just wondering because I got an earring that would improve HP/Mana but I don't want to use it if it is worse focus wise for our DoTs.

[Xnao]

only spells the raid one extends by a tick are the 1:18 base ones. the 30 sec base get extended by like 4-5s

[Noobieguy]

Hmmmm, so it wouldn't be that big a deal, unless I am trying to do the 18 DoT rotation. But if I just use an extension pot, it fixes that too! Hadn't been using the extension pots, just got a fresh supply (Thanks Volg and Gaid).

[Siddar]

All DoT's should gain +8 ticks. +1 from det ext focus +1 from potion +6 from AA DoT ext. Never been able to see a actual increase in number of ticks between the group focus and raid ones every time ive tested them.

I just view all det ext earings as add +1 DoT tick focuses doesn't matter if its group raid are partially decayed.