Talk:Thunderlord's Decree/@comment-3974211-20161109040257/@comment-30295538-20170701161140

Exactly. Thunderlord's is preferred due to its amplification on burst damage and the ability to often win lane. It's more powerful on champions that can proc it with quick succession (multiple abilities plus a ranged attack, like most mages) while Deathfire favors champions like Rumble, who have a ridiculously high DoT potential and can demolish a large area in a team fight.

In fact, as you stated, late game most mages would benefit more from Deathfire, but the advantage Thunderlord's offers early game makes it difficult to gamble.