Strange issue with Ice Block and Ragnaros

Posting this here because the last time I posted a general issue it got moved here just because I was using a Mac.

Playing a game and the opponent had a number of minions out. I had Majordomo Executus and an Ice Block secret active. The opponent attacked me, bringing me below 1HP and triggering my Ice Block, making me Immune. He then turned his minions against my Majordomo, killing it and turning me into Ragnaros. His remaining minions then focused on me. (This was all within the same turn.)

Now, once becoming Ragnaros, I no longer had the Immune glowing outline. Whether that’s correct or not, I don’t know, but I did take damage from the other minions…except they could not reduce me below 1HP. They had enough to kill me, I think they did about 12-15 points of damage to me after I became Ragnaros, but I did not go below 1HP.

This feels like a bug because either 1) I should have died, or 2) I should have still been immune and not taken any damage after becoming Ragnaros. Again, this all occurred within one turn. I died next turn when I failed to draw a solution to his minions.