For example, if it blocks a 12/12 creature with trample, that creature's controller must assign at least 8 of that creature's combat damage to Diamond Weapon, and the remainder can be assigned to the defending player, planeswalker, or battle
Artifacts are listed last (well, other than lands) and Yotian Soldier, at the time, was the last artifact creature alphabetically
If you play a high land count, you risk not drawing a high enough quantity of spells to double-spell as often as you need to
Either way, this card won't set you back too terribly if you know it's calling your name
Treebeard, Gracious Host There are ways to gain absurd amounts of life in Magic, meaning Treebeard, Gracious Host is able to make one of your creatures massive or spread the wealth and buff them all