This is what I do against Kenshi... Seems effective, but probably because most Kenshi players are garbage.
Seriously about 95% of the kenshi players I've played just stand there and hold block waiting for you to try something predictable and punishable. So, I just get as far away as I can and chuck a few ias. The kenshi player will then start either tryign to reflect the sais, or use tele-flurry. You can then either telekick the wiffed reflect or telekick his tele-flurry. Then you're in.. at this point with at least one meter bar and you get to start the mixup game. After landed telekick, you could start with the 42 pressure, u4, or my experience is that very few players react and block b3 EX roll correctly.
See how he reacts after your combos.. compensate accordingly... (that goes for like, every matchup regardless of who you're playing).
Against raiden what I do is dash forward and keep doing fd4, which makes mileena do D4. Tap blocks in between to stop him from supermanning your face. If you use fd4 instead of just pressing d4, it makes you auto punish his teleport by instantly hitting it with a roll.
More to it than just those tactics which are probably widely known / countered now though.
I still have problems against KL and Jax.. They're beatable, but jeez, even mediocre players that use KL give me matches that are much closer than they should be. I know what to do against him, but I'd say it's one of Mileena's worst matchups. Smoke and Ermac can be troublesome too if they know what they're doing.
but yea.. it's definitely not true that mileena has no bad matchups. that's just silly.