You're listing your funds you're invested in, but that's not saying how much of what type of fund you planned to hold, and your reasoning for why and what your goals are, etc.
So: you need to figure out how much of what type of funds you want to hold, based off of your goals/risk assessment, etc... and to figure this, may also help to figure out your investment policy statement to help guide you.
Reading material:
https://www.bogleheads.org/wiki/Asset_allocationhttps://www.bogleheads.org/wiki/Investment_policy_statementhttps://www.bogleheads.org/wiki/Principles_of_tax-efficient_fund_placementIf you are wanting a super simple 80/20 stock/bond holding in index funds, then you're just needing to sort out which is closest to the lowest cost available in your accounts (if unable to use VTSAX and VBTLX across the board). And yes, trying to figure out when the market may or may not be running out of steam is a fool's game. Just figure out a nice and simple index fund portfolio, figure out your goals and triggers and get it all properly laid out in an IPS and refer back to it in times of worry; that's your blueprint for the future no matter what the markets do, follow your own path marked down and you'll likely end up where you planned to be.
And if you're using Vanguard's index funds (VTSAX and VBTLX for the most part), then you are already diversified quite nicely. Index funds are by their very nature "buying the entire market" so they contain thousands of companies currently trading. They are the definition of being diversified.
So as far as figuring an AA and rebalancing...
For an example, I have my asset allocation set to be:
75% stock
10% REIT (real estate fund)
10% bonds
5% cash (high interest savings acct)
I have in my IPS that I don't rebalance until it's out of range more than 5% in any direction and I'll check it at most every 6 months. So a few times a year, I'll run the numbers and not bother if it's only 2-4% or so. I use Squawkfox's
free excel rebalance sheet (4 square US couch potato).
If it is out of range, then I sell the high flyer and buy the low/sale priced of the funds I chose to hold to get them back into acceptable range; and I make sure to do so in the account(s) that are going to be the most tax efficient (like I'll only have my bonds in a tax sheltered account). Very simple.