No i am not talking about their final fight, I am talking about their fight in Kyoto, If Cao Cao didn't have phoenix tear at the time, he would've done for when Issei cutt off his arm.
Cao Cao is not Ikki yes, but he is still a very skillful fighter who trained his entire live and had prior knowledge of what Issei is capable of plus he is specialize in deflecting and dodging.
Issei being able to handle Cao Cao proves he certainly have a basic idea how to hendle Ikki here especially if Ikki didn't use Ittou Shura right away and if Ikki did use Ittou Shura Issei can simply takes flight and the scenario I mention above will happen.
Issei fight and defeat Cao Cao twice, Kiba, Saji, Sairaorg Beal, Shalba Beelzebub, Barakiel, Thanatos, Vidar, Rizevim, he also would've defeat Dulio if it wasn't because Dulio's team ending the game beore Ise could finish him, Nyx, and he match Vali a prodigy who trained ever since he was a kid.
All those people have years, possibly hundeds or even thausands of years of experience ahead of Ise, have a means to literally one shot him, nullfy his power, some of them is even stronger then him at the time most of them also have prior knowledge of what Issei can do, his strength and weakness, and even his fighting style, etc and yet Issei match and defeat all those people in hand to hand combat by his ingenuity and skill.
Saying Ise is not a very skilled hand to hand fighter, for a lack of better term and sorry if I am sounding rude, I think is very ignorant.