Typical goblin. AC 15. Lae'zel at level 5 has To Hit of +5. Damage is 2d6+3 with Greatsword. She faces typical goblin without GWM. 10 or higher is what she needs to roll to hit. 55% chance of success. Damage is between 5-15. Typical goblin has 7 HP, roughly. So good chance that if you hit, they dead anyway, but at least your chance of hitting is 55%.
With GWM, same enemy, chance of hitting is 15 or higher which is a 30% chance to hit. That's a significant reduction in a person's ability to hit. Damage potential is 15-25, sure - a 100% chance to lob the goblin's head off and get an attack with a BA - but how much less often are you going to hit? 25% less often.
So isn't that kinda a trade-off? I could attack as normal and hit 25% more often for 5-15 damage or hit 25% less often for 15-25 damage.
It is a trade-off, yes, but GWM is always optional which is a huge benefit of the feat. Also, be careful about your percentages. With a base 55% chance to hit, GWM (-5 for a 30% to hit) will hit (55%-30%)/55=45% less often (almost half), not 25%. Alternatively, a normal hit will hit (55-30)/30=83% more often than GWM (almost 2x), not 25%.
- Without GWM (using 1d12+3 because it has a uniform distribution=easier statistics) you have a 75% chance to deal at least 7 damage, and a 55% chance-to-hit. 0.75*0.55=
41% to OHKO a goblin.
- With GWM, you have a 30% chance to hit and 100% chance to kill.
30% chance to OHKO a goblin. But you get an extra attack if successful.HOWEVER, goblins in BG3 have closer to 13 AC and 10 HP (unless things have changed since I last played/heard)
- Without GWM, you have a 50% chance to deal at least 10 damage, and a 65% chance-to-hit.
0.50*0.65=32% to OHKO- With GWM, you have a 100% chance to deal at least 10 damage, and a 40% chance to hit.
40% chance to OHKO.GWM wins straight out.
Again, GWM is optional so you can tailor your attacks to each enemy's AC and remaining HP.
Your math is correct in your particular case (for greataxe though, greatsword would average 7 points of damage, not 6.5), however there are couple more things to consider.
1)
In BG3 your base damage will be higher than in PnP, mainly due to magic weapons that add damage on hit and/or dipping weapons in fire, coating them with poison. The higher your base weapon damage is, the greater the effect of lower attack hit-rate is, and the smaller gain +10 to damage is.
In case of level 4 Lae'zel that uses Everburning Blade with 75% hit chance the difference between ASI and GWM would be:
- -5% damage per round with GWM on normal attack,
- +18% damage per round with GWM on attack with advantage.
2)
While calculating the effect of getting bonus attack on reducing enemy to zero hitpoints is hard, GWM feat also gives you a bonus action attack on critical hit. So we just need to modify expected damage by +5% in case of a normal hit, and +9,75% in case of advantage.
So in your given example (Great Axe base damage, 75% hit rate) the differences would be:
- +12% damage per round with GWM on normal attack,
- +49% damage per round with with GWM on attack with advantage.
While the difference is minuscule for a normal attack, with advantage it's definitely notable.
3)
Combining considerations in points 1 and 2 - Lae'zel, lvl 4, GWF, Everburning Blade (or any dipped/coated 2d6 weapon):
- +0.1% damage per round with GWM on normal attack,
- +28% damage per round with with GWM on attack with advantage.
So even in 75% hit chance case, which should be highly favorable to GWM the difference is not big enough to consider the feat OP. At 60% the gap would be -9% and 6% respectively and at 45% the damage would be better without power attack on and difference due to -1 Strength would be -12% and -5%.
In conclusion in BG3 specifically GWM is not overpowered choice for two-handed fighting style, but it's a good feat that competes with ASI. Would I take it for Battlemaster Lae'zel? Probably not on level 4 or 6, but on level 8 most likely. For a Wildheart Barbarian? As soon as possible.
If Larian adds PAM, that works the same way it is used in PnP and/or Variant Human (no sacrifice on Strength score for getting a feat) then my opinion would change.
That all said, if OP asked are two-handed weapons too good compared to two weapon fighting or swoard and board, my answer would be yes, especially after getting Extra Attack. In addition the feats the other styles get are a lot worse than GWM.
Good points all. Specifics of BG3 monsters, weapons, and abilities, as well as the extra attack due to getting a crit, are relevant.
The takeaway seems to be:
GWM is nigh-universally better if you'll frequently have Advantage on attacks, but is much less effective (ranges from being slightly better to slightly worse) if you're attacking at normal.I've never done the math, though, so I'd like to thank GM4Him for that.
>:(
