"...half of the available space is tied up in those 'big blocks' so the rest of the world is really limited on available space."
"Big block" landlords are still holding out for big users. This includes 800 5th, 2nd & Seneca, Macy's, 1201 3rd, Russell Investments Center, Yale & Thomas, Elliott Bay Office Park, 520 Pike, 83 King, 1600 7th...etc.
Until large portions of these spaces start leasing, landlords will be less likely to entertain smaller multi-tenant floor deals, which means less inventory for more normal sized tenants (for now).
For normal size tenants, i.e. the rest of the world, it is tough to find good spaces in the <15,000sf realm. This is because half of the available space is tied up in those "big blocks"; so the rest of the world is really limited on good options.