sum copy and past
http://forums.d2jsp.org/topic.php?t=67041534&f=87Dru:
Tier 1: Raven, Poison Creeper, Wearwolf, Lycanthropy, Firestorm
Tier 2: Oak Sage, Summon Spirit Wolf, Wearbear, Molten Boulder, Arctic Blast
Tier 3: Carrion Vine, Feral Rage, Maul, Fissure, Cyclone Armor
Tier 4: Heart of Wolverine, Summon Dire Wolf, Rabies, Fire Claws, Twister
Tier 5: Solar Creeper, Hunger, Shock Wave, Volcano, Tornado
Tier 6: Spirit of Barbs, Summon Grizzly, Fury, Armageddon, Hurricane
01 ≤ iLvl ≤ 11: T1, T2
12 ≤ iLvl ≤ 18: T1, T2, T3
19 ≤ iLvl ≤ 24: T1, T2, T3, T4
25 ≤ iLvl ≤ 36: T2, T3, T4, T5 (D2C: iLvl ≥ 25)
37 ≤ iLvl ≤ 99: T3, T4, T5, T6 (D2X only)
+6 Oak helm is impossible.
But +5 Oak is possible.
Affix level 50 (+2 druid skill) doesn't mean item level 50 :
a high quality level Pelt may have affix level 50 with low item level (low enough to spawn Tier 2 skills, like Oak).
You can produce a low item level rare Pelt with :
- rolling recipes ( 6 p.skulls, or 1 p.skull + 1 SoJ)
- imbuing
Aim at item level 12-18 for the best chance of spawning +X Oak.
Dream spirit with item level 12-18 has affix level 71,
Sky spirit with item level 12-18 has affix level 67,
Earth spirit with item level 12-18 has affix level 53.
Since those recipes only work with rare quality items, you cannot do the same with magic Pelts.
Hence +6 Oak isn't possible (+3 to Summon is a magic-only affix).