Drys give better single target dps but the lance gives you AOE.

This has been a misconception for a long time, I think from before the Legacy update (in the same update, most abilities got significant changes to their damage/cooldowns/effects). It's time this stops being regurgitated.

https://youtu.be/jIiiFpa7w48?t=184

There's almost no scenario where you would choose dual wield over 2h melee. Not only does Quake debuff make up the difference for most bosses, a lot of boss mechanics favor burst damage over a long channeled ability. For example, Araxxor special attacks (get damage in before reflect or being interrupted by cocoon) or being walked by a boss like Vindicta which cancels your channel, or the boss moving out of range. Dual wield is really only good for using Keris or Darklight. If you really want the extra DPS, you can bring Drygores simply for using Destroy, and more specifically using Destroy during Berserk. And if you're going to do that, you might as well abuse the fact that Cleave and Decimate do not share a cooldown as well.

Best single target is using both, if you have to/want to only use one, use 2h. I really dislike when people are given incorrect/incomplete advice.

It is important to remember that we're talking about Slayer (I went on a tangent about bosses to talk about single target DPS), and just as you said, you absolutely want the AoE.