With the new patches and changes coming, Modafinil is now basically 20 seconds duration on 45 seconds CD in PVP and raid (which is all endgame TOS has to offer).
Since the skill requires a lot of investment in contrast to e.g. Trot (i.e. you need high SPR, skill level and enhancement attribute level), I think it’s not very fair to make it a skill with a high downtime on content that actually matters for invested people.
A good solution for the problem would be the introduction of an attribute to fix the situation.
Similarly to chronomancers Pass:Focus Time, Modafinil becomes a self-buff, but has its skill duration increased (e.g. outside of raid/pvp the duration increases from 60 seconds to 300 seconds, inside of raids/pvp it increases from 20 to 100 seconds).
Similarly to cataphracts Trot, Modafinil has its duration kept intact but it’s buff value cut in half in pvp/raids. No attribute needed here, people still happy.
Modafinil becomes a self-buff and receives a party buff attribute similarly to kabbalists Ein Sof:Double Magic, reducing both duration and effect on all party members by 50% of the initial value.
This would make the skill last 30 seconds with 45 seconds CD with the attribute active.
Introduce a new Art for Beak Mask that increases the duration of drug-based skills (Methadone and Modafinil) when used while wearing the Beak Mask.
All 4 options make for viable balance changes that allow the person playing plague doctor to have the control over his buff while providing some sort of balance for harder content that doesn’t render the skill completely useless for the plague doctor himself.