Some thoughts on Attack Per Turn / Sneak Attack / Colossus Slayer / Ripostle

[Eothain]

While I was thinking about maximising a possible multiclassing Fighters damage, I kinda notice that Ripostel+Colossus Slayer ( Opponent not with max HP) or Ripostle+Sneak Attack are actually viable and valid high damage attacks. Both Colossus Slayer and Sneak Attack are per turn so a Fighter with 3 lvls of Rogue or Ranger should in theory highly increase its reaction damage output. Just a thought ! Am I missing something ?

[RealDealBreaker]

Yes, both sneak attack and Colossus Slayer can be be triggered multiple times in a round (specifically twice - once on your turn and once when/if an opponent triggers an attack of opportunity which uses your reaction). That said, sneak attack is far superior of the two when you are looking to multiclass a fighter. Why? Well going ranger doesn't unlock Colossus Slayer until level three (and only if they choose the hunter archetype) and a fighter doesn't get much benefit out of the other level one and two features granted by ranger. Taking three levels for an extra 1d8 (average 4.5) damage that will usually only trigger once per round (attacks of opportunity are relatively rare).
Going for rogue as your second class for sneak attack is better. Sure, sneak attack at level 1 (and 2) rogue is only 1d6 (3.5 average) but a level 1 rogue gets expertise in two skills. Expertise is way better than favored enemy and natural explorer (the ranger level 1 features). At level 2, rogues get cunning action which allows them to disengage, dash or hide, as a bonus action (in pen and paper 5e these are usually actions, in BG3 this benefit is less applicable becasue disengage/jump is already a bonus and cunning action got moved to the thief archetype at level 3 rather than base rogue at 2). A bonus action disengage or dash is going to be more useful in general than ranger level 1 spells (2 slots, best spells take concentration and as spells are limited by slots regained on long rests). And if you take three levels of rogue (i.e., same level investment as getting Colossus Slayer), sneak attack increases to 2d6 (average of 7, 7 > 4.5 from Colossus Slayer) damage AND the rogue would also get the level three feature(s) from the subclass of their choice (whereas a ranger is locked into Hunter to get Colossus Slayer) which is a huge bonus (in pen and paper, in the current build of BG3 it is a much smaller advantage because only thief and arcane trickster are in).

TL;DR: Both are valid and viable, but fighter rogue is better because their features overlap less with fighter than ranger and sneak attack can be unlocked from a one level dip rather than the three required to get Colossus Slayer from the Hunter Ranger.

[Eothain]

Very well put... I quite agree with the Fighter/Rogue MC and planning to build a (Fighter 5/Rogue5) at full release.

The Ranger MC has different intention. This one would be a Dueling Fighter6/Defence Ranger4 thus maximum possible AC build to enhance misses as much as possible, leading to more Ripostle attacks. It is a thought experiment and more or less something I tried on Gith Patrol extensively. One can get 24 AC for a short period of time using Potion of Speed and Shield of Faith then within 3 turns Gith Patrol is down, Btw this is a solo build. I realzied lately that I dont even need GWFs extra attack for more attacks.