Guard Press does require a Grass Energy as well as a Colorless energy to use, making it a bit of a slower starter than some other EX Pokemon. It deals 40 damage and during your opponent’s next turn, any damage dealt to Heracross EX is reduced by 20 damage after applying Weakness and Resistance. This can make him a decent little tank.
His second attack, Giga Power, requires two Grass Energies and one Colorless Energy. It deals 80 base damage, but can deal 40 more damage if you deal 20 damage to Heracross. 120 damage for 3 energy is perfectly acceptable.
Overall, Heracross EX is a solid EX card. His Mega form is also definitely something to be reckoned with. If you see a Heracross EX hit the table, make sure you deal as much damage as you can to him before his Mega form comes down! Along with his Mega form, Heracross EX is definitely worth of being at the heart of a competitive deck!