To get an idea of what buffs are strong and what are not, I skipped through all buffs and here is a list:
[Party] means the skill is applicable to other players, while [Solo] is only usable for the caster. RX means the earliest rank you can have this buff at least at Lv1 is rank X.
__Damage buffs
R2 [Party] Enchant Fire (Pyromancer): +7 Fire Dmg, +7 Additional Dmg (Lv1) - +34 Fire Dmg, +7 Additional Dmg (Lv15)
R3[Party] Sacrament (Priest): +12 Holy Dmg, +12 Additional Dmg (Lv1) - +40 Holy Dmg, +40 Additional Dmg (Lv10)
R2[Party] Blessing (Priest): +15 Additional Dmg (Lv1) - +70 Additional Dmg (Lv15)
R5[Party] Weapon Maintenance (Squire): +1~6 Attack (Lv1) - +15~90 Attack (Lv15) (depend on weapon’s stars)
R4[Party] Swell Left Arm (Thaumaturge): +34 Phy+Magic Atk (Lv1) - +154 Phy+Magic Atk (Lv15)
R5[Party] Swell Right Arm (Thaumaturge): +40 Phy+Magic Def OR +34 Phy+Magic Atk (Lv1) - +121 Phyl+Magic Def OR +111 Phy+Magic Atk
R2[Party] Zalciai (Krivis): +12+SPR Crit Attack (Lv1) - +100+SPR Crit Attack (Lv15)
R1[Solo] Gung Ho (Swordsman): +8 Phy Dmg, -2 Phy Def (Lv1) - +50 Phy Dmg, - 10 Phy Def (Lv15)
R1[Solo] Concentrate (Swordsman): +5 Additional Dmg (Lv1) - +26 Additional Dmg (Lv15)
R6[Solo] Deeds of Valor (Doppelsoeldner): +10% Atk, -10% Def (Lv1) - +10%~+150% Atk, -10%~-150% Def (Lv15) (15 stacks possible on Lv15)
R3[Solo] Finestra (Hoplite): +10 Crit Chance, +2% Block, -8 Evasion (Lv1) - +150 Crit Chance, +30% Block, -39 Evasion (Lv15)
R5[Solo] Frenzy (Barbarian): +11~+22 Atk (Lv1) - +20~+400 Atk (Lv10) (2 - 20 stacks)
R2[Solo] Kneeling Shot (Archer): +15+DEX Phy Dmg (Lv1) - +52+DEX Phy Dmg (Lv10)
R2[Solo] Sneak Hit (Rogue): +62% Crit Chance (Lv1) - +90% Crit Chance (Lv15)
R5[Solo] Steady Aim (Ranger): +7 Additional Dmg, -15% Attack Speed (Lv1) - +34 Additional Dmg, -1% Attack Speed
__Stats
R2[Party] Monstrance (Priest): +? DEX (Lv1) - +? DEX (Lv15)
R3[Party] Divine Stigma (Krivis): +15 STR, +15 INT (Lv1) - +78 STR, +78 INT (Lv10) (need to kill mob)
R6[Party] Swell Brain (Thaumaturge): +25 INT (Lv1) - +45 INT (Lv5) (up to +100 INT bonus from attribute)
R4[Solo] Transpose (Thaumaturge): Change INT and CON
__Defense
R2[Party] Aspersion (Priest): +20% Phy Def (Lv1) - +48% Phy Def (Lv15)
R5[Party] Armor Maintenance (Squire): +1 Phy Def (Lv1) - +15 Phy Def (Lv15)
R6[Party] Barrier (Paladin): +10 Magic Def (Lv1) - +50 Magic Def (Lv5)
R5[Party] Increase Magic DEF (Pardoner): +50+SPR Magic Def (Lv1) - +260+SPR Magic Def (Lv15)
R5[Party] Swell Right Arm (Thaumaturge): +40 Phy+Magic Def OR +34 Phy+Magic Atk (Lv1) - +121 Phyl+Magic Def OR +111 Phy+Magic Atk
R4[Party] Stone Skin (Priest): +0+SPR4 Block (Lv1) - +480+SPR4 Block (Lv5)
R2[Solo] Guardian (Peltasta): +10 Phy Def, -14 Phy Dmg (Lv1) - +35 Phy Def, -63 Phy Dmg (Lv15)
R3[Solo] High Guard (Peltasta): +150 Block, -50% Atk (Lv1) - +240 Block, -50% Atk (Lv10)
__Other
R6[Party] Arcane Energy (Oracle): +3% Max SP, +9 Max STA (Lv1) - +45% Max SP, +65 Max STA (Lv15)
R2[Party] Aukuras (Krivis): +21 HP Reco, -3.6sec HP Reco Time (Lv1) - +105 HP Reco, -6.4sec HP Reco Time (Lv15)
R4[Party] Restoration (Paladin): +100 HP Reco (Lv1), +337 HP Reco (Lv15)
R2[Party] Daino (Krivis): +1 Additional Buff (Lv1) - +15 Additional Buffs (Lv15)
R2[Party] Divine Might (Cleric): +1 Skill Level x1 (Lv1) - +1 Skill Level x10 (Lv15) (x1 = 1 times)
R6[Party] Haste (Chronomancer): +5% Movement Speed (Lv1) - +7% Movement Speed (Lv10)
R5[Party] Quicken (Chronomancer): +30 Attack Speed (Lv1) - +450 Attack Speed (Lv15)
R6[Party] Special Force Formation (Centurion): -50% Cooldown (Lv1) - -50% Cooldown (Lv15)
R5[Party] Undistance (Scout): +? Attack Range (Lv1) - +? Attack Range (Lv10)
R6[Solo] Evasion (Rogue): +10% Evasion (Lv1) - +100% Evasion (Lv10)
R3[Solo] Quick Cast (Wizard): -10% Cast Time (Lv1) - -50% Cast Time (Lv5)
R4[Solo] Samediveve (Bokor): +149 Max HP, +2% Movement Speed (Lv1) - 485 Max HP, +6.5% Movement Speed (Lv15)
I left out some special buffs like Protection Zone and stuff.
I wonder what the difference between Physical/Magical Attack and Additional Damage is.
Please let me know when I missed some buffs.
Thaumaturge buffs seem so strong… xd
