Im not 100% sure about the role of Sliver Queen in the list, but beyond being an iconic and extremely fun card to include, it likely serves as a win condition in control mirrors, where both players tend to trim down on removal and games often go long
While Howler could just make himself huge with a wheelwheel and win with commander damage, the combat damage rider makes you actually want to spread his ability out, as does common sense saying that anyone could just chump block your 19/4 Shark Pirate
If you can give her haste, you can then use six of that mana to reactivate her ability and rinse and repeat
The mana value of a split card is the total mana value of both halves of the split card added together
This meant they had to be proactive, not reactive, and they had to be effects that were generally useful at most times of the game
These allow you to craft more cards you might desire, thus converting into more cards for your collection