Harder to target, but hardly incredibly difficult. You're making a judgement based on trying a controller on game for one day, what's more, on a game that you've already developed associations and habits for.
I played XI on my PS2 for a while in the earlier days of the game, but I couldn't imagine playing without a usb keyboard to go along with the controller. It required way more inputs than DAMP, even ignoring the need for communication. I had like 40 macros I needed for that game.
Just like you had 40+ macros for XI on KB, and others that never gotten that deep into the input system can't imagine how its like when they only play controller, you don't realize all the incredible things that can be done on KB because you've never experienced them.
I've played plenty of controller games before. I would do far worse without KB&M on a lot of kits and builds. Due to factors other than input, I'd still be able to do reasonably well, but it isn't nearly as good, and I'd be restricted to certain builds and playstyles-- just as you would trying to go from KB&M to Controller only on XI. Your skill ceiling is much lower because of the input device limitations. There's still lower hanging fruit available, but it isn't nearly as much.
The same is true of Breakjohn with playing fighting games with controller vs fight stick. The change of input device allows much finer control.
In my case, it is the reverse direction. Change of input device here makes for much coarser control, and lower skill ceiling. I'd have to adapt a more brute force / lazy gameplay style or accept dying more / playing on lower difficulties.
For the record, I played a round of perilous and a few of NM with the controller, was still top score but just barely in some cases.
If camera control and targetting was better, (I can't even automatically match targetting of my teammates), the controller would be much more compelling.
Note: I've seen how most console players play. They are sloppy, and it makes sense now why given how imprecise the controller is.