I'm pretty sure your vision of the game is wrong. And that's very good news for you.
Let me explain, you seem to understand dota, the items and farming, etc ... From HoN you probably have better reflexes than 99% of Dota players, and solid farming mechanics.
On the other hand, let's be honest, most of your build are complete shit. And I say that because, if you manage to win with that ... you would stomp with the correct items.
For example, your necro headress to dagon ... what ?
One of the most easy build on necro is to just rush meka, and become a healing machine, also meka resolves your problem of armor in early game. Don't hesitate to go teamplay on necro, meka, urn, bloodstone, are efficient items on this hero to help in teamfight, survive and push. Also they all give tanking, which is the best way on necro to carry. Snowballing with a dagon is an option, but honestly it just relies on a skill gap between you and some players of the enemy team, and that's never a good idea in the long run.
And overall, you seem, like many players, to care way too much about having many items, and especially doing a lot of damage.
You do gimmicky items often, like travel, dagon or eul, when those are often situationnal or mid-lategame items, and in most cases you're missing HP or just a bkb.
Let's take some concrete examples,
http://www.dotabuff.com/matches/1141231346 You should have a wand for sure here, and have went bkb instead of lifeleach and all your other stuff. I mean it's cool to have lifeleach, but just being harder to kill and able to take out one target (like silencer) is important with DK. Also BKB prevents PA from blinking on you, it's pretty big. On this hero, confort is often suicide, lifeleach and such is cool, but you can rarely rush it. I advice treads-wand-drums and then to addapt on him. I've a decent winrate with him if you wanna check my builds http://www.dotabuff.com/players/5901147/matches?date=&faction=&hero=dragon-knight&lobby_type=&game_mode=®ion=&duration=
http://www.dotabuff.com/matches/1141173372 Doom is a hero that needs to adapt, and even if vlad is cool, often you want to get something making you really usefull. Here, just replacing that with a dagger could have changed everything, since you could have just blinked and doom silencer straight. Since I believe he must have been a big Issue in fight. With one less hero and no silence to fuck WR or Skywrath, you could have gotten more in early game.
http://www.dotabuff.com/matches/1126317829 Maelstrom first is shit, period. Maelstrom isn't a bad item, mjolnir is often great as a 3rd or 4th item. But first, it bring nothing you need, on most heroes. Wr can benefit a lot from just phase boots, a wand (here you have bottle so wand isn't that important but I like it on her) , and a force staff or a meka, and your hero would have bene much more potent in fights. You seem to focus on yourself when you clearly are the one that should make "supporting" stuff.
http://www.dotabuff.com/matches/1048062688 You should have a bkb or a HoT here, the fact you didn't do any tanking or protecting is very wrong, I mz