As Shaeeck said, if you are receiving quality training from qualified instructors this is a good combination. The TKD offers the stand-up training, while BJJ covers ground work extensively.
it is if you are receiving quality training in each style and not just training for competitions. point scoring don't win self defense situations. you cannot scream at the man mugging you "hey i hit you that is a point to me"
how else would u be training withing maiming each other ?
so yes this is a deadly combination but not the best
look into jeet kun do with is a mix of eastern and western philosophy
combined into a deadly art...
good luck
Would these two make a good mixture for self defense?