Tychus plays the "Assassin" part rather well. Is easy to play and deals a lot of damage. This bulld focuses on his trait rather than on his abilities. Overkill, grenades and run and gun are only perks. First, we need to make sure to make Tychus to last more than he does with Doc on the bed in the battlefield. For that reason, Master Regen is the first talent to be picked. Armour Piercing Rounds comes to second, but later in the game, you become a walking overkill machine so this talent with his ability becomes redundant.

After reaching level four you go with Vampiric Assault. Focused Assault comes to second, and it makes sense to deal additional damage to heroes, but without vampiric assault Tychus won't last long in team fights, and he needs to be in team fights in order to be effective. No solo engagements.

After that Rapid fire is the talent of choice, further increasing your attacks to 5.6. That's a lot of damage, and later in the game you start dealing a lot of damage to both heroes and non heroic units. Sizzling attacks comes to second, but I prefer having more attacks constantly than just a burst of damage, because this Tychus is meant to be in team fights, Heaven's Devils style. Drakken laser is better, because it doesn't interrupts the flow of your auto attack and provides additional damage output and a rather inconvenient distraction for your opponents. Best used in objectives or decisive team fights.

Now, I have two builds I play with most, depending wether the map allows for landing or requires intense team fights like Cursed Hollows. If you are going to commit to teamfigths, Problem Solver is best because the bonus coupled with your 5.6 attack becomes 2.7% of bonus damage, depleting your opponent's heroes health bar and most of the time, killing them within seconds.

Executioner then becomes the only viable talent to pick, since we are talking about dealing massive amounts of damage. Works best if you teammates that deals a lot of stuns and slows. And then, to finish the game as the top assassin, Nexus Frenzy.

That's it. You'll become a walking overkill machine. Is true. With 5.6 attacks that with Nexus Frenzy is upped to 6 and with Stim pack temporarily upped to 6.5, you are dealing more damage than with Overkill, while remaining in battle most of the time. You need quick health? Just go to a lane with no enemies and recharge. Need to clear a mere camp? You can do it within seconds after reaching level 13. Need to take boss? Well, you aren't that strong but you can finish off a boss with just a willing tank or another assassin. For that, you'll need your drilling laser and you are all set.

Stimpack is best for lane heavy games, like Tomb of the Spider. Problem solver when you want to commit to Team fights.