I'm 90% positive this wasn't an issue before the hotfix last night.

Currently, you can hit another action before your cast completes, and when the cast is done, you'll use the second action. But you can't do it for the action that applies the card's buff.

Example:
  • Begin casting Benefic.
  • Hit the input for Draw 0.5 seconds before Benefic ends.
  • Draw casts immediately after Benefic finishes casting.
  • Begin casting Benefic II.
  • Hit the input for Bole/Spire/etc 0.5 seconds before Benefic II ends.
  • Benefic II ends, buff is not casted.