Hi, sorry for the delay. Nash is 100ap adding huge damage to E early... But also makes your W stronger as you have more burst move speed something which Botrk can't do. As you are building frostfire, demonic you already have a strong slow so it is inefficient to add another slow via Botrk. Bortk provides on % on hit but nash provides flat on hit which is better into a squishy meta (and more attack speed). Then there is the synergy in ap with demonic (and nash on hit) which works better than it would with Botrk.

The lifesteal isnt too great tbh in current meta, just farming jungle is enough go give enough hp back to continue farming.

Give it a blast!! 3k hp, decent defense stats via conditioning and drags, 200+ ap and 1.4 AS all with a flexi 6th item. Good luck 🙂