Fleet work can be easily proc'd with just an auto almost every 9s (charged at lvl 1 just by walking) and provides 30% bonus movement speed for 1 second, the same amount of move speed as the Heal summoner spell
I would say this rune offers more movespeed per game then the Phase Rush movement speed buff of 15% - 40% for 3s, requiring 3 seperate attacks or abilities to proc it. (Unfortunately, the in game rune panel for Fleet Footwork only keeps track of how much you have healed, it doesn't tell you how much time you spent hasted. It would be useful to have this metric to compare it to Phase Rush).
Eventually at lvl 11, Phase Rush matches Fleet Footwork's 30% move speed buff. Surely with 3s haste you cover more ground, but by lvl 11 Fleet Footwork has done much more for your laning phase (the most consistent part of the game) than Phase Rush. Also, the move speed bonus for Phase Rush depends on experience and level where Fleet Footwork's move speed bonus is constant throughout the entire game.
In defense, one might argue that Phase Rush provides 75% slow resistance but this is a specific benefit with a big payoff in less scenarios, potentially not at all; where as Fleet footwork's heal is a general benefit that is useful in more scenarios, almost all the time.
Maybe Phase Rush is better late game, but still it seems Fleet Footwork can be proc'd multiple times in a single fight, providing similar benefits for much less effort and cooldowns, especially when stacking Energized items.
I would argue there is too much move speed given for Fleet Footwork procs.