D&D 5E Deadly Strike with Weapon Mastery

[Axel]

A question came up in a recent playtest game. How do you play Weapon Mastery interacting with Deadly Strike? Two interpretations argued at the table were:
- Roll an extra die for each damage die and choose the higest from each pair. (For a longsword damage roll 2d8 twice and choose the highest each time).
- Roll an extra die once and once only. Thus the same example, roll 3d8 and choose the best two.

For speed and simplicity we ruled one extra die only - otherwise the high level versions would take longer than the last packet's Scorching Ray to resolve. Any thoughts or opinions on what you or your group consider the correct interpretation?

 

[jadrax]

According to the Feat; Weapon Mastery only allows you to ever roll one extra Die per damage roll, no matter how many dice you roll normally. Deadly strike adds extra dice to the Damage roll, it does not increase the number of damage rolls you make.

Although as an aside, this wording means that if you were using a weapon that did 2d6 damage, you would only roll 3d6 and drop the lowest - which seems wrong.

 

[Plaguescarred]

As jadrax said. A 5-level Fighter with Weapon Mastery that hit with a long sword deals 3d8 + modifier and drop the lowest d8.