They often rely on cheap flicker spells like Cloudshift and Blur as both value engines and win condition, so you can invest in other places
Then when you swing with Tanazir you can have the base power and toughness of everything that you control become your Elder Dragon's power and toughness, so without any additions to the guy you'll get 4/4 base and power to your team
Its all upside for you, working on opponents life totals and making your creatures easier to cast
Since Mais ability causes life loss and not damage, this even works through The One Rings protection in older formats, so opponents cant use that to get around it
A good amount of times, your card draw will be an ability of a creature, enchantment, artifact, land, etc