Featherfoot sucks, for any class. For starters you assume with RNG that featherfoot would be better for a bard, but let us take a step back and remember bard is ranged and should not really need to "tank" anything other than maybe a slime on t1. Now with that in mind, there are certain attacks that can be parried, but never dodged (twintania's fireball just to name one). Now featherfoot on my warrior sucks, it purely sucks with a dodge rate on even lesser geared content such as prae, wp, hm primals, it cannot dodge at all so the result is the same for bard, you will more than likely never dodge, but you shouldn't be tanking as a bard either. Now this topic is about mantra for bards and no, mantra at 5% sucks for bards, maybe if it stacked with monk for that 1 time in the fight of 2h or whatever you want to call it, spike damage, but let us be honest, monks mantra is more than enough. So for bard, mantra is a no, featherfoot is a no and keen flurry because of the random target attacks that can be reduced by it is by far the greater skill for the 5th slot.