Personally, I don't think philo stones are required on Brand. I have a hyper aggressive play style and I don't require any HP regen at all and only need one mana regen item. I'm comfortable farming and killing early game and I purchase items to increase my damage output.
So to respond to your build,
It is possible to farm and harass without philo stones (+regen). Brand won't benefit much from upgrading the philo stones so the Gp5 will serve as a small loss or at best break even on the money spent on the stones. Consider buying Kage's pick if you would like a Gp5 item (it may also be possible to upgrade it depending on the enemy team comp). Buying a philo stone or two does mean you're sacrificing a potential increase in damage output.
That said, build whatever you like and whatever suits your style of play. If it doesn't work for you, it doesn't work and vice versa. Experimenting with builds is useful and fun. There'll never be just one way to build a champion because there are so many factors in every game that make it different (team composition, laning partner/opponent, etc)
The philo stacking is a fun build and it's good to see it being played with on different champions. Remember that philo stacking is for fun unless your champion takes full benefit. Champions that greatly benefit from philo stacking (and max cdr) include Alistar and Taric becase they enjoy increased HP regen, as well as CC, healing and have great survivability (the list of benefits goes on) and can benefit from the upgraded versions of up to 2 philo stones.