The newly added warmup timer seem to cause a DC when using "Scroll of Past Deeds" to teleport directly to Garrosh. Have tried with nothing but BigWigs active and still get DC everytime.

Your report is appreciated, but there is a zero chance this is related to BigWigs.

You can try disabling BigWigs and seeing if the issue still occurs, or waiting for another day to see if it's a server issue.