is xerath worth it?

xerath will get absolutely obliterated by hard engage and tanks. if the enemy team is squishy or isnt great at running at you, then he is good

He great in a poke comp, and probably the best poke mage in this meta along with AP Koggles (out of and maybe ). His range is insane, but he has low kill potential until late mid game and if you get jumped on, you have a problem.

If you are good at positioning then yes. You can be just as effective in team fights from over a wall (or two) which is nice. He has a slow and a stun which are also nice, but absolutely no disengage, or shield like defensive abilities. If you are ganked and you miss your stun you are either dead or down a summoner, so make sure you take Flash, and either Heal or Shield. (I prefer to take heal due to the small move speed boost).

Every single ability he has is a skill shot, and in my opinion his Ultimate it too easy to dodge, and doesn't do enough damage. But, if you snowball you will feel like a God.

In my opinion (!!!), Lux is a better choice. She has a shield, a snare, and slow and her combo of Q, E, R is easier to land, and It will Delete carries even with few items. Not to mention her ultimate is SOO much easier to land, does more damage, and has a shorted CD.

Kog'Maw is better at poke, in my opinion.