I did try it, my mate still play it and it's really easy, even him who play WoW from start say it's alot easyer now, no instance ever is going to be hard and funny as Naxx, deal with it..
They do it to get more subs, I don't even best guilds want encounters like the 4 horsemen in classic Naxx anymore. In TBC/WoTLK they allowed noobs to buy epics with tokens and pvp gear through honor, in classic if you weren't in guild that could do 40mans you were stuck in blue gear = cancelled sub for a lot of people. They made it more casual but it's not necessarily a bad thing, some encounters in wotlk and cata were still reasonably difficult.
And it wasn't impossible, it was just to hard, my guild killed him amongst first after that patch, but soon after that like 80% of guilds who was on him killed him just after couple trys, even Twins became harder then him after that patch. They make game easyer so ppl who don't know to play good don't stop playing (and most ppl sux tbh).
Well, this happened long ago, so i'll take your word for it, but I specifically remember some encounters being made impossible so blizz has more time to develop content, classic rag and cthun immediatly came to mind 'cause I remember the massive amount of crying going on and top guilds threatening to cancel.