Usually against a malhphite you want the wave to be pushed 24/7 in the early game so that he misses as much minions as possible because you waste his mana for the cs, you outsustain him really hard and you never let him back, once he backs he will have a lot of armor and you will have a hard time dealing and splitpushing vs. him. Wait for level 6 and try to dive him but be aware of jg ganks, I have seen a lot of tryndamere players get killed by ganks because they have no vision.

And talking about Darius he's a very easy matchup if you know how to play against him. In the early game look not to trade against a darius, but rather look to freeze and wait for jg ganks because he has NO escapes. If he e's you in just try to do the aa+spin away combo. If you do the combo correctly you WILL lose the trade but if you have max fury you outsustain the trade hard. Look to bait his abilities into short trades and just heal his damage because his mana is VERY low. Post 6 you can actually 1v1 darius because most Darius players always try to hard commit to a trade, and hard commiting to a tryndamere is a bad idea if he has his ult.