I don't know about the other characters, but as far as a HC rifle-using Katarina goes, a guide is virtually irrelevant --- except for how to get by a few bosses, like Rajani, Ehregott and Chakti, and there almost everything else also seems irrelevant apart from dodge-dodge-dodge-hit-dodge-dodge, and a few specific strategies, like taking Rajani's fire form up close and dodge-rolling from one place to the other when she teleports.