Buying forma is kind of a waste unless you want it RIGHT NOW for some reason. T3 void missions have a 33% chance to drop a BP, and any void survival missions have a decent chance at forma/forma BP. If you farm any sort of prime equipment or frame you will probably end up with more forma then you can ever use.
Uh, no. Been farming for Prime stuff for the last month and a half. I'm pretty confident on what the drop rate is, and it's not high enough to meet my needs.
So far I've used.....over 30 Forma, excluding what it took to build the Dojo (which I ponied up almost entirely myself, TYVM.) When you factor in needing to farm keys, the RNG, the credits and the mats for Forma BPs....buying them makes plenty of sense. Yes, it's a choice to pay for the convenience and pain removal. I'm already farming the void as it is and every Forma gets made and used pretty much as soon as I get it. And rather than rotating a bunch of crappy weapons until I do get some Forma....I'd rather just spend some plat to buy it, and keep on with the weapon I'm currently paying attention to.
And yeah. V is a worthless polarity slot for most Warframes. What's really annoying is most frames start with a V in the Aura slot....which gives you exactly two choices: Rifle Amp or Steel Charge. Forget that Energy Siphon, Rejuvenation and the Ammo Auras are the only ones people use.
On the other hand, for weapons, V is the most important slot bar none.