I prefer shiv over PD on varus but I agree that shiv isn't really core. Like said I play Varus mainly for Q damage and wave clear so for that purpose shiv works better then PD. If they have a full AP comp or a heavy CC comp you would be much better off getting a scimitar over a GA but I do agree it's situational. As you can see in the items though it's listed under "Situtional defensive item".

Far as W start. Blight still does 10 extra damage at level 1. It doesn't only do damage if you activate the % damage. So like I said in the guide it can help for last hitting at lvl 1 when you are at your weakest or if you do end up trading a couple auto attacks it's still extra damage.

There's no other offensive item that will be better in the end than a BOTRK for a 6th item if you are going full offensive. I suppose maybe if they had a heavy stacking armor team you could go black cleaver but in most cases BOTRK would be the best 6th time if you aren't getting a defensive item. If you think there is a better item I'd be interested to hear what. The health is nice just can't spam your Q as much if you don't take the meditation points though.

Yo, few points:

I don't think statikk shiv is a core. It's replaceable by phantom dancer and generally I think it is a better choice for most of the cases. Also merc scimitar is kinda situational, guardian angel fits in every situation.

Double lifesteal in full offensive is kinda meh :/
W start gives you nothing to start with. You can't use it without second abilitiy, so starting off with Q or E is much better. Meditation is not worth, take the health in defensive imo.

Also the guide is very short, so it could use for more information and chapters.
I'll give you +1 as it's your first guide I think, so you get lil motivation boost :3

Activcating comment to vote means that you have to add comment usually including the reason of upvote / downvote, so you can know what to improve. Without comment to vote, you can't know why you are downvoted or upvoted. It can be activated from the right tab in guide editer (it's fully optional tough, so it's not must)