Spamming 2 wrath for 1 starfire (with dots) will make you benefit 50% of eclipse, and eclipse is less than 50% uptime. Overall boomkin can be atleast 80% efficient as a soloplayer, by spamming 1 button and timing starfall/cd. To be fair, boomkin is one of the best and easyer dps to macro with good result, like arcane mage, still not all the advantage of Spriest as class stacking.
Starfall is always very nice to have.
Boomkin also put the +13% magic damage on the target passively when casting on it, wich is better than the warlock curse (and easyer to handle too since it's passive)