The feeding does not increase the difficulty. Building training ground and mercenary camps do not increase the difficulty. Those who are arguing against the fire phoenix are citing an action that has little to do with anything. Feeding the phoenix adds 5% per evolution level to your attack strength; it has no impact on anything else. Keep in mind that people have only used the phoenix for two tournaments at most, and those that thought it was broken on one have reported the opposite on the other.
I think things were also heavily skewed due to the 'first' tournament people were using the new Red Chocobos was the asinine Scrolls tourney which is 110% rigged entirely against the players due to;
a) the enemy has 0 weaknesses, so there's no viable 'counter unit' for you to bring - anything you bring is auto hard-countered in return... as well, the enemy is 100% ranged, so, enjoy the dreaded alpha strike BS too!
b) the terrain generator seems to go into full-on "feth-you" mode and many of the fights are actually unwinnable as there's just no way to overcome all the ganky barriers. (some are so bad that even your own ranged units are screwed!)
c) the AI is beyond stupid when using
your units, but it's an absolute genius when controlling the Shady Characters.
Silk is probably the easiest of the 'moderate' difficulty tournaments, though Humans will have more trouble vs. Elves. (mainly due to Pallies being hosed by crappy anti-light infantry stats)
More telling I think will be if/how much they help out with the 'moderate' difficulty tourneys such as Plank, Elixir & Dust.
I haven't put my own birdie down yet, but those in my fellowships who have seem to be finding that they're working as intended now.