I've made this argument a dozen times, but here goes.
Shields, engines, sensors, and regular systems stay online. The lights dim as an indication of cloak, just like red alert doesn't mean they transfer power from the non-red lights.
Shields would appear to drop DURING the cloaking process on some older model ships, but not on newer ones. Weapons in the show come on-line nearly instantly. They take time to repair, and theres a cooldown while they reload, but generally they can fire right away after red alert.
ECM would defeat the purpose of cloak, so it would hardly come up.
I still stand by how Taldren chooses to represent cloak, as its more balanced than actual cloak. DS9 is hardly reliable, the Defiant would have been given an out-of-date model. You have to go by how we've observed actual ships.
We've seen cloaked ships be lit up by explosions without taking damage. So, they have shields.
In the episode where Geordi is kidnapped by romulans, they show the warbird decloaking, tractoring immediately, and firing. There's no point decloaking to run these operations unless you have to, therefore we can determine that, while they can tractor and fire immediately after cloak, they cannot do either while cloaked.
So basically, think of cloaked ships like U-Boats. They're not any more or less vulnerable when cloaked or decloaked (surfaced or unsurfaced) except for difficulty to hit. They can't really do a lot under water/cloak, but they can be good and ready right as they surface/decloak.
Alexander