In my PoR hard mode I used Ilyana from the chapter you can recruit her to endgame. I really didn't think she was that bad. Sure, in the later parts of the game, Soren completely beats her in every way mostly because he can double enemies while Ilyana can't.(at least in my walkthrough; its possible my Ilyana got speed screwed) This means Soren can OHKO most enemies for me near the later parts of the game. However, I rarely saw her accuracy go below 100 even with bad biorhythm, and is very reliable accuracy wise. Also, most enemies besides mages have lower resistance than defense, which means Ilyana was quite useful to me. She could survive most physical weapons like handaxes, bows, javelins for me so as long as I heal her up, she will be ready next turn to fight.
I just finished Part 1 of RD in JP hard/EN normal mode and from what I have played from Ilyana, I am probably not going to use her. The speed problem from PoR was here again, but this time, her accuracy was in the 50s at times and there is no way I am going to trust take units with that bad accuracy. Heck, even Micaiah, who I read from most forums that she was not a good unit, had her uses of killing armored units with Thani and weaken enemies reliably since her accuracy was very high. Can't say the same for Ilyana for this game.