This is terrible for concentration, but it's bad for a number of other things too - folks may have noticed that slipping or falling prone at any point during their turn causes them to lose their entire turn immediately, regardless of what they were doing or what actions they had yet to take; this is why.
Ouch! I had a variation of it in my recent playthrough that annoyed me so much I reported it over to Larian:
My Sorcerer and Pal had joined turn and a troll was right after them. Sorcerer casted ice cantrip on troll and blood under him turned to ice. Pal and troll both slipped. Even though I didn’t even touch my Pal his turn was skipped, as he was part of the joined turn, while troll got up, crit the pal and killed him. Good times.
