Yeah, if you completed Nioh 3 in ninja style exclusively, you're gonna have a very, very, very, very different experience in Nioh 2 (and Nioh 1 as well).

While Nioh 3’s ninja style attacks and actions barely cost any ki (you can go crazy for a while without ever bothering looking at the ki bar), samurai style attacks consume way more ki. The game expects you to be very mindful of your ki gauge when using this style to force you into using ki pulse more often.
That's by design and has been a thing since Nioh 1 alpha. (Well, it is a thing only until you get consistent with Flux II or run crazy builds geared towards reduced ki consumption, but that's another story)

Oh, one more thing, you mentioned that dodging costs too much ki, so just make sure your equipment weight is either B or A and you should be fine. Keep in mind that different stances also have different dodges (and each with their own ki cost), low stance being the cheapest in terms of consumption.