4th level Rogue

[hellmonkeyd2]

So there I was, planning my next session for 5e in what has been a now 7 month campaign. The session was to include a group of assassins aimed at killing off an important aristocrat the PCs were turning a quest in to. I built a 4th level Rogue with the assassin tree and the great weapon master feat (so as to get an executioners axe). I then tallied the numbers on a medium and max damage roll with the character and noticed something rather over the top...

Assassin's Death Attack Makes you crit if you win initiative.
Great Weapon Master lets you get a second attack if you crit, that due to the nature of Death Attack is also a crit.
All of this applies Sneak Attack.

This topped out with some pretty unreasonable damage.
I don't have the sheet on hand but it was ballpark ~70 -> ~100

question now is, has anyone else found something this unreasonable? if so what?

[1337 b4k4]

Slight correction to your math: You only get the critical as an assassin if your target is surprised. Otherwise you just get advantage.

[da_chicken]

Sneak Attack is limited to once per round, but otherwise that looks right.

So you've got 12 (max) + Str + 6 (max sneak) + 1d12 (extra crit) for the first hit, and 12 + Str + 1d12 for the second. You have advantage on both attack rolls, but the second only happens if the first one does. Assuming Str 16, you're looking at 22-33 on the first hit and 16-27 on the second, so 38-60 damage.

Compared to twin short swords no feats:

So you've got 6 (max) + Dex + 6 (max sneak) + 1d6 (extra crit) for the first hit, and 6 + 1d6 for the second. Assuming Dex 16, you're looking at 16-21 for the right hand, 7-12 for the left. That's 23-33. So, unsurprisingly, a Great Axe doubles your damage.

Crits are supposed to change somehow in final to be less damaging, but I've heard too many different versions to guess what they might be.