The Spirit Realm

I have been told that Tonic of Efficiency (I to VIII) potion extend the duration of our dots.
Can I just take any of these of these potion that would extend any dots by 1 tic at least (even with level decay), or do I need to take highest one (VIII) for 80+ dots ?

Thanks

I thought minimal increase is always 1 tic ?

Any pot will increase length by one tic as long as atleast any extension remains after degradation.
lets presume you use the potion with
2: Limit: Max Level(70) (lose 5% per level over cap)
at lvl 85 it would have lost 15*5 = 75% of its effectiveness, so still some effect remains. That means you get your tic more out of it.
If you take the lvl 65 pot, it does work up to lvl 84 dots, but excludes the lvl 85 ones.

So: Tonic of Efficiency Affinity V gives +1 Tic for all dots upto lvl 89

For heal over time spells the same is valid for Tonic of Regeneration Affinity V: + 1 tic for all hots upto lvl 89

So it there any reason to make the higher lvl pots? Will they ever give more than 1 tick extra for hot or dot? It doesn't look like it but my math might be off and I am missing something.

The higher potions will have better effect on long lasting spells. The bare minimum will add a tick to everything, but will add actual time to long effects. Malosinea, disease dots if you use em, things like that. Same with buffs. 1 tick to HoTs/Lynx, because of rounding, but higher potions will add actual time to buffs.

Various melee in my guild have taken to soloing RSS for AA while it's a hotzone. Plowing a million of that level mob generates tons of Versluierd Fungus, they forward that to me and I <3 them for it.