This feature has been requested for a long time now. Unfortunately Crate is standing firm and usually the advise is to use the Mythical Codex of Eternal Storms. I love Wind Devils too and together with a good crafted Stormsurge Pistol and Yeti offhand MI, it’s really fun playing to have high uptime on Wind Devils tbh.
I still don’t like WD but it’s not like we don’t have options. If your build uses them only for resistance reduction - you don’t need more than one on the field (since they usually clump together anyway so your coverage is the same). If your build uses them as damage then… press that button every 4.5s to deal more damage - just like every other build and/or use an items that gives you burst summon, increases their duration.
Also, afaik, if WD are in your build for damage, you want to constantly resummon them anyway because of Maelstrom.
Perhaps a transmuter that makes them permanent but reduces their damage by 95% would be an elegant solution. This way WD could function both as Guardians and as damaging skill. TBH I would like Guardians and Blade Spirits to be the same way - you can either have them as a passive, permanent DoT or make them short-lived but deal more damage.
I was just thinking about this yesterday while playing my Elementalist. I have Hand of Ultos attached to wind devil, which is freaking amazing because 3 of them together crit way more often than most attacks. But you can’t do this with the item-granted wind devils, so that option is useless to me. I think if wind devils were permanent, they would have to be nerfed a bit, but seeing that the devs don’t want to make them permanent, I think they should be improved in other ways. Like not stopping to cast (seriously, wtf), and a small signal for when the cooldown has ended. Maybe I’ll make a suggestion post for this.