Not only can the Broodmaster create a lot of tokens, but those tokens become larger the more mana you invest into it. It is a double X cost, which means you need to have quite an available investment to pump into her. But pouring even 8G into the ability, a reasonable sum for a Green deck in the late game, gives you 4 4/4 Hydra tokens, plus an 11/11 Broodmaster. That's quite an end-game weapon.
Obviously, some players saw the Broodmaster as a big target for all of the colorless mana that Kruphix, God of Horizons can help to collect for you. At the time, it was still certainly one of the better Hydras that had been printed at rare outside of Mistcutter Hydra - a big deal sideboard card at the time. Unfortunately, Kruphix Ramp decks, even aided by the Prophet of Kruphix, never made much noise in Constructed.
However, Hydra Broodmaster would not find herself limited to being a bomb in draft. Hydra Broodmaster would in fact enjoy some competitive, top table Standard play. Three 2014 State Championship decks ran a copy of Hydra Broodmaster as a finisher in their Mono Green Devotion builds, including this 2nd place finisher in Maryland. She also found herself in several Top 8 Magic Online Standard decks, including this tournament winner that ran one copy of her in the sideboard.
While Hydra Broodmaster only had a short time in the Standard sun, in Commander she has since joined forces with the very same Kruphix, God of Horizons that people thought she would team up with in Standard. The Broodmaster appears in a great many Kruphix decks. Other Commanders that have welcomed her into the fold include Omnath, Locus of Mana (who has plenty of mana to spare), Trostani, Selesyna's Voice, Selvala, Heart of the Wilds, Rosheen Meanderer, and many others.
Hydra Broodmaster may never be an expensive card. But the Clash Pack promotional foil is always trending upwards. Also, sales consistently being made on the regular printing, so there is non-zero demand for this creature. It's a good one to pick out of bulk boxes, for sure.