Sirzechs in the last episode of the anime seems content that Issei took Rias away from the engagement ceremony and even Grayfia notes that he seems happy about the fact that it's "unfortunate" that the Gremory and the Phenex clan will not have any marriage whatsoever. The reason why he's happy about it is because it reminded him of his and Grayfia's circumstance when he married Grayfia, one of the servants of the Old Lucifer and at that time, it was a big no-no.
Issei Does Not Know His Own Strength. Normally this can be shrugged off as Heroic Self-Deprecation, but during the Mid-Class exam he attacked another low class devil (who may or may not have had the power to become mid-class) in Balance Breaker. If he had boosted at all, he would have blown the other person, an ally, in two.
CaoCao implants himself with a Medusa's eye to replace the one Issei shot out. What happened to the Gorgon?
Issei's motivation is to become a high class devil so that he can gather a harem of female servants that he can have sex with. He essentially wants to become a Serial Rapist that constantly engages in Sexual Extortion of his subordinates and nobody has called him out on this or even noticed the Unfortunate Implications of his goal.
Unfortunate implications aside, Issei has proven through his interactions with the girls that surround him that he is respectful of the girls as individuals with their own thoughts, feelings, and ambitions, proving that you can lust after a woman but still understand there is a person underneath that physical beauty. Hell, Issei has even outright rejected the (often times aggressive) sexual advances of the girls surrounding him because of some issue that led him to believe it was inappropriate at that time. This track record would lead us to believe that even if he had his own servants he wouldn't abuse them.
Not to mention the fact that one of the first big fights was against Riser shows that Issei does truly value the feeling of each woman unlike Riser who does it just to have women.