RE: 6.5x284
It should be a fine deer cartridge. The case is shorter than a 30-06 but much fatter- it holds about 2gr less water than a 30-06 case. 6.5mm bullets especially 120gr and up are superior to .30 bullets in my opinion.
I don't have a 6.5x284, but shoot a cartridge that is a .284 case necked up to .30, which was most likely the original cartridge that gave Winchester the inspiration for the .284 as there isn't another american cartridge like it- 7.5x55 Schmidt-Rubin