This is one of those combos... wow...
It can be used once, maybe twice, per day. It is not a game breaker unless the DM literally only uses 1 encounter per day, and then, only if there is a single vastly important entity involved in that fight. If the DM builds encounters like I do, then usually there are no "OMG! Kill it!!" creatures involved. Instead, there is a team of enemies working together to end the PC's lives, or capture them at least.
Also, this tactic does absolutely nothing when the only encounters the PC's face in a given week is social encounters, lol... The game isn't always about combat.