The trio join former contestants Kelly Brook, Austin Healey and Mark Ramprakash on the 32-date arena jaunt, which kicks off in January.
Bastian, who found fame in Hollyoaks, scored full marks for her Viennese waltz on Saturday and is one of the favourites to win this year's show. Cassidy, who will return to her role as Sonia Fowler in EastEnders next year, scored 31 points for her quickstep at the weekend.
Ex-Footballers' Wives star Zoe Lucker departed the series earlier this month after scoring 33 for her foxtrot and American smooth.
Len Goodman, Bruno Tonioli, Craig Revel-Horwood and former judge Arlene Phillips will be at the live shows to rate the celebrities' performances.