It's not about L2P. I don't understand why you even felt the need to bring it up. A pity you did, actually, because it kills any objective discussion that could be had. Let's ignore you said it, for the sake of this thread.
Let's make that twice better, because Vi benefits most from HP. Phage is 60% of the cost of an Elder Lizard, meaning you have about 1k (actually that's 700, I didn't count machete) left to spend on that Black Cleaver, and Black Cleaver is worth twice as much as Elder Lizard. While the CDR is nice, the hp/5 or mp/5 doesn't do anything for Vi. She hardly needs mana after her first Blue and the HP regen is a long term benefit, while stacking more HP is a double dip on any engage due to her shield and Vi stacks BC stacks very quickly.
I feel that your entire take on Vi is from a single target pure burst perspective. Will R + Q be enough on a single target, actually, yes, most of the time, but it doesn't help you chasing leftover targets. And you're not always in the position where you have several allies that can stop any runaways.
Vi benefits from all stats on Phage. Double from HP.
Vi benefits from all stats on BC. Double from HP.
Vi only benefits from 2 of 4 stats on Elder Lizard and it has no HP.
The way I play Vi, she can be focussed in the middle of an engage and still stand straight. The way you seem to play Vi (early) is a glass cannon build, which will work when focussing down a single target and you will rack up kills faster, but if you're caught in an ambush or just happen to walk into anything that's better at focussing down single targets (Xin comes to mind), you will wish you had that hp. My Vi also helps my teammates get kills or assists by slowing anything that ends up running away.
So all in all, agree to disagree I guess Just don't make silly comments about L2P. It's so..1998.