To clarify, because increased percentages-to-hit can confusingly mean one of two things, I believe that @OP is talking about absolute percentage.
E.g., a non-hidden fighter has a 70% chance to hit, but with Hidden-Advantage has a 91% chance to hit. Out of 100 blows, they'll hit 91-70=21 more times than they would otherwise.
Another way of phrasing this is using relative percentages.
E.g., a non-hidden fighter has a 70% chance to hit, but with Hidden-Advantage has a 91% chance to hit. Every attack is (91-70)/70=30% more likely to hit (1.3x multiplier), higher than the 21% bonus in the first example.
Thanks for the clarification, I was indeed talking about your first example !
Regarding Lvl 5 and up, I meant more in terms of raw damage output, and the need to mitigate this with chance-to-hit:
- a rogue with sneak attack will use their single action to deal (assuming hit and a standard shortsword) 1D6 + 3D6 + dex modifier at level 5 (granted, advantage will apply to all as it's all dealt in one blow).
- a fighter with 2 actions (assuming something like everburn blade or sword of tyr, disregarding the damage bonus) will deal 2D6 + 2D6 + 2D8 + 2*str modifier (with something like frightening attack).
The damage discrepancy is big enough without fighters having also an almost guaranteed advantage on one of these attacks. I don't mean to whine, I also enjoy fighters a lot, but I fear rogues will feel a bit underwhelming after level 5 in terms of raw gameplay experience.
