My strategy was basically to hoard as many tokens as I could, and every time I get a blackrock foundry mission I upgrade the 3 followers that counter best to 675. On my lock I have so far 5 at 675 and 12 at 664 (thee latter ones have only their armor upgraded as I have a severe shortage of weapon tokens), whereas on my main shaman I have 6x 675, but still sitting on a bunch of tokens that I haven't used. I honestly just follow what these addons tell me to do, without them I have no clue.