No, I do not agree with that.  You can certainly mine with 1.5TH and receive payouts on a frequent basis.  I have my miners split into groups at roughly 2Th/s and they are just fine, averaging .02 - .03 BTC / day and a share every 3-4 hours.

I don't get your graphs though.  Your graphs are showing numbers in the GIGAhash range - 7.65Gh and 1.32Gh - not anything close to a TERAhash.  Given the numbers in your graph I would expect to get little to no payouts.

It is my belief that currently you can mine successfully on P2Pool with an S3 and get reliable shares and payouts.  Yes, that seems to be a high barrier to entry but unfortunately I don't think that's going to be very avoidable very soon with general difficulties increasing.