You make a thread about difficulty, knowing well you're using two pretty big mods that change the difficulty of the game, and you complain about some of the responses you are getting. And being very impolite to Notserious80 on top.
I don't know what you were expecting. This would've been such an easier issue to deal with if there wasn't any mods in play, but no.
Even on Very Hard, at level 17, it is simply impossible for those two guards to be that much difficult to deal with. And this isn't even counting the fact that you can knockdown both of them with Jackie.
The only reason I can think of to not stealth knockdown them (because I do it myself) is wanting to level up a different skill than Ninjustsu by killing them "manually" with a weapon. Is that the reason why, just for a little bit of context?
Have you managed to kill them by now, since you posted this thread? If yes, what about the following fight sections of The Heist, is everybody else also giving you trouble there?
If no, then as mentioned above, there has to be something going with your mods, perhaps even after removing them. At this point this everything all of us can try guessing about your issue here, because again, you are over-leveled for the area, pistol spec'd on top and using one of the best guns in the game (assuming you're using Kongou ; unless you added another weapon to your inventory through the console).