Whenever I play in lane as Garen against Darius, I can not do anything, unless my Jungler ganks allowing me to get ahead, because only then can I deal even or more damage then him, I am not trying to say Darius is broken or something, it just seems I can never beat Darius without my Junglers help and that seems strange, so am I doing something wrong?
Darius has traditionally been the better laner when paired against a Garen, it's been this way for awhile.
You're best bet is to stack armour early against him and hope to out-tank him. At level 6-8 you should be be able to put up a decent fight as your ultimate has easier access to damage than Darius, especially if assisted with a gank
I think Garden does pretty well vs Darius . I play close to him so when he winds up his Q instead of getting away push in on him with Q,E,W so he can't hit you with the edge annouy his CS and he usually dosent try to AA you when you are spinning on his face. Go for cinder into Sunfire first. Other option is you know Darius is going to bully just let him push/greed and have jungle come get dat booty.
Garen is more bursty and mobile than darius. You will lose every prolonged fight, but win every short one.
Save your Q cleanse effect for his W; he's going to most likely W you so you're slowed when he tries to land Q. Your safest when playing around the Q blade area, but you don't want to stay in for long fights. Keep count of his stacks on you, he will be doing the same. If he gets to 3 and has either Q or W off cooldown, you'll probably want to leave the trade. If you use your W's high block at the start of it (it's like 60% right?) on his Q, you can block the majority of his damage, since he will most likely be maxing Q.
Darius is the kind of champion who can dictate when and where fights happen, but you with the Q slow cleanse can get around that, which is honestly a huge part of his damage potential.
Stack health and armor, but health tends to be more important imo, since he has passive ignore armor and will probably buy cleaver for shred, so he reduces the efficiency in flat armor or armor-heavy purchases. Tabi also helps.
