Not only are you getting a large creature with a good effect and reach, but youre also getting a second creature that gets stronger as the game continues
Even on its own outside of a Pirate deck you still have a two mana creature that can flash in and block an opposing attacker, acting like a removal spell that pairs favorably with all of the ways to reanimate creatures in Standard
Not only that, but it leaves a lingering annoying effect in play which can hose both commanders and value engines
More importantly, Valgavoth, Harrower of Souls ability makes it so that anytime an opponent loses life for any reason, it gains a +1/+1 counter, and you get to draw a card
Arthur is fine, but nothing to get too excited about
Phyrexian Tower I suspect that we have a few cards in Ultimate Masters that some folks mistakenly thought were on the Reserve List