My luck was not exactly on a single pack but I actually did 3 arenas on a single day (never play arena) and after that I got 3 packs and some gold (wnt 7-3 9-3 and 4-3) and on those 3 packs I got 3 legendaries back yto back to back, got Jepetto Joybuzz, Catrina Muerte and Swapqueen Hagata so that's pretty lucky I guess, specially since I already got all the super good legerndary from RoS and was planning on saving gold for the next expansion since that point (or at least not spent more gold on packs).
I've been playing since beta and have never had 2 legendaries in the same pack. I've never had legendaries in consecutive packs. The best I ever got was a legendary and an epic in one pack.
I'm not envious. I just want two legendaries in a pack!
Which means I just want what you've got.
OK, I'm a little envious.
According to gamepedia, you can expect to get 2 legendaries in 1 pack in 4 out of 10k packs. I do not think there is any pity timer in place either, like there might be for golden legendaries (250-300 range.)
It happened to me once, but expecting it to happen again would only make me disappointed...