I have been on and off WoW for about 8-9 years usually just to get a few containers, I regularly try my luck. I have ever only had 1x super container. Officially 'try your luck' increases your chance of getting a super container by 2x. the numbers (if I remember correctly is 1% standard, 2% if you try your luck (might be 1.5-/3%).
I have had thousands of containers, and the last super container I remember getting was over 5 years ago. and its not like I dont even spend on the game. The ultra grind approach they put on this game is scandelous and from my experience seems to break the law (in EU/UK) on gambling especially where real money is spend on resources which is in turn spent on items of 'chance'.
