I'd say they're good, depending on the situation. Suppose you're against cryo abyss mages or fighting a cryo domain. If you're affected by cryo, your stamina consumption rate increases. In this situation, if you have a movement speed buff from your weapon's passive, then you'd be able to dodge an upcoming attack. There's one weapon, "Skyward Blade", in Skyward weapon's series, which gives movement speed buff when the character uses its burst. I've been using it on my Jean, and with its energy recharge stat, my Jean can have 100% uptime with her burst.