Over the last week i have seen this happen MANY MANY times. A boss will have a normal pip at start of round / then when he casts is changes SUDDENLY to a power pip / thus allowing him to cast a higher pip spell /
there is no issue, boss's have the same chance of getting a power pip as the rest of the players.
I think Razgar meant something like this.Say you were in the middle of fighting a boss.The boss has two normal pips,but when it casts the spell one of the bosses pips turns into a power pip,lettting him summmon sunbird instead of fire elf.I have never seen, it just be your screen.
boss begins the match with 1 white pip and casts thunder snake. The next round the boss gets a power pip and casts storm bats, and thus making you think that the boss somehow cheated