In a well balanced comp where you have 2 tanks or 1 tank and 1 brawler-assassin you should go for the first build since it wont leave you too vulnerable at the same time as you can dish out a lot of dmg.

You should always be behind the front line and within enough range to spam your fel flame.

Try to focus whatever target has the lowest health pool since your burst can even kill tanks as longs as they don't have a lot of spell-block.

As long as you're safe life-tap before every spell-cast (especially your life-drain since your not dependent on your teams support for healing) and use your drain life when you're around 30-50%hp.

The second build is very valuable when you're facing great pokers and your front-line isn't very strong.

Try poking the enemies with flame and corruption until they're below 50%hp where your life drain really shines, it has quite the cool down which means you have to beware of when's the time to use it and make sure you're in range and there's no enemy to stun you.

Good to focus on enemies who are slowed or stunned.

Third build is used for ***** and giggles really, or if they have a very tank focused game and you can stay safe for the entire time.

It's really a fun build where you just try to focus spamming your q as much as possible and maxing your dmg output.

Just keep enough distance for fel flame and spam it simply.

General stuff:

Fel flame:
Your low CD-skill and nuke, to be spammed when there's space for life-tapping and life-draining without risk of getting killed.


Drain-life:
After mana tapping down to between 30%-70% of your hp (depending on you are in; safe zone, safe enough zone or danger zone) this comes handy.
In fights make sure you are in range and not too exposed or focused and use it when low on hp.


Corruption:
This skill is a dot, which means that you shouldn't expect it to burst down people but rather peel them.
Use this as an initiation since the CD is quite long where you know the path they're heading to get all 3 of the dots in.
Be careful using it since if you have the lvl 1 talent you need to get as many hits as possible on as many enemies possible in order to get the reward.


Horrify (Ult.):
This one can be used for both defensive and aggressive maneuvers.

For initiation;
try to get it slightly behind an enemy in order for them to run towards your team while at the same time try to get it in front of the enemies whom you want to zone out from the fight.

For example if your team have the damage necessary to burst down an enemy tank (who's most likely on the front-line) you can cast it right between the tank and the rest of the team to get the tank running in your team eating your damage while at the same time the rest of the team will run in opposite direction and thus reducing the risk of a full 5v5 teamfight.

For escape or counter attack;
you can use it to save your teammates. For example; an ETC has your 4 teammates in a rock show and the rest of the enemy team is on their way in their to clean your team up you can use it to completely neglect his ult making him run towards you while the rest of his team will flee the other way.
Make sure you're in the back line not getting caught by some strong counter against you like Diablo, Varian, Mura or other strong initiator.