To be honest, I believe merc lord can be substantial enough on some maps to swing games. I believe if sylvanas is nearby a bruiser and siege camp on haunted mines, the advantage is more than double a 60/40 or 70/30 split if sylvanas is nearby to help the push. I believe the life drain or follow through are the only other talents and both are weak unless you play sylvanas as "hold the q" ( this is very ****ing wrong, you are a bad sylvanas and need to switch heroes if you are not manually using the q ability 90% of the time ). Outside parenthesis, it is that ****ing important.

I like this guide. I have yet to try it but given your estimation of Sylvannas's low DPS, I think a push build centred around Mercenaries is the way too go. In solo Queue, this build would be especially strong because many people don't do Merc camps as much as they should in Solo Queue for some reason.

I wonder how good she would be with a bribe ability? Or does she even need it?
And how efficient is Mercenary Lord? Since you have to be around them, its hard to evaluate the skill.