After a patching process that seemed to take hours (possibly because I was playing another game while I waited), I spent a couple of minutes in LotRO to see the class changes in Helm’s Deep. (I am only 45 so I am nowhere near seeing the content of Helm’s Deep.)
It looks like all they did was integrate industry-standard "skill trees" into the game, so you have to choose one of three specializations for your character. For my Hunter, I got to pick from a Jack-of-all-Trades tree, a Ranged DPS tree, and a Traps-base tree. I don’t mind the change but I do think it makes LotRO gameplay a bit less unique. Not something I would rage quit over, though. Who knows, maybe it will bring in some new players.