Changing up my Karthus Style

So, I've just hit silver 1, the highest i rank I've ever hit to date, and it came off of a 5 game winning streak where I changed up my style of playing Karthus. Part of it was the lateness of the hour, but I still managed to get promoted playing with a much more reckless style. Basically, mid to late game, I was playing a lot more loose and not worrying too much about dying as long as my ult was up and it wasn't an isolated pick. I also switched my build up for late game finishing off with a Luden's Echo and just trying to have as much damage as possible. I was basically a big nuke late game and after each win I was first in the game in damage dealt, even though my KDA was on average 10.8/8.4/11.8, which is dying a lot more than I usually do. (especially if you take out one game that ended early where I only died 3 times, that really boosts up the deaths average.)

At the end of the day the question I pose is, is this a legit way to play Karthus, or did I just get lucky? It seems like later in the game dying as him just isn't as bad if you die in the right place and can get your ult off afterwards.