coolAlias
Explorer
Here are some things that can provide an extra (usually reaction-based) Sneak Attack opportunity:
From this list, it seems clear that the vast majority of reaction-based SA opportunities require either a feat investment or resource expenditure (superiority die or spells).
The feat-based reaction opportunities are also situational, some more than others, so that it is unlikely to occur every round (but potentially could with good positioning and tactics for e.g. Sentinel).
Rogues must also consider that they only have 1 reaction per round, so all of the above compete with Uncanny Dodge and any other reaction-based features the rogue might have access to. The only one that does not require the character's reaction is Thief's Reflexes, and that only comes online at 17th level.
What all that says to me is that granting a reliable second SA each round, especially one that does not use the character's reaction, is something that should only be done with extreme caution, lots of play-testing, and player feedback.
That said, it's your table - do whatever you want.
- Attacks of Opportunity (very DM / tactics dependent)
- Sentinel feat for more reliable AoO plus when an ally is attacked instead of you
- Mage Slayer feat grants AoO against spellcasters within 5 feet
- Readying an Attack allows extra SA opportunity when hasted
- Battlemaster "Commander's Strike" maneuver from an ally
- Battlemaster "Riposte" maneuver gained via multiclassing or Martial Adept feat, enemy must attack you and miss
- Thief's Reflexes (Thief archetype only at level 17) grants two turns on the first round of combat unless you are surprised
- Orcish Fury feat when you're dropped to 0 hp but not killed outright (XGtE)
- Hydra
From this list, it seems clear that the vast majority of reaction-based SA opportunities require either a feat investment or resource expenditure (superiority die or spells).
The feat-based reaction opportunities are also situational, some more than others, so that it is unlikely to occur every round (but potentially could with good positioning and tactics for e.g. Sentinel).
Rogues must also consider that they only have 1 reaction per round, so all of the above compete with Uncanny Dodge and any other reaction-based features the rogue might have access to. The only one that does not require the character's reaction is Thief's Reflexes, and that only comes online at 17th level.
What all that says to me is that granting a reliable second SA each round, especially one that does not use the character's reaction, is something that should only be done with extreme caution, lots of play-testing, and player feedback.
That said, it's your table - do whatever you want.
