Weird, I've used Global HUD timers in my own game just fine. how exactly are you implementing them?
FYI Here's how I have it set up in mine, mine has the HUD scroll upward out of view. Although you could easily do the same with opacity
HUD > 0
Set Each hud piece to lerp(X,32,dt),lerp(Y,32,dt)
Set HUD to Clamp(0,10, HUD-dt)
Set Each hud piece to lerp(X,-32,dt),lerp(Y,-32,dt)
On Even to Bring up Hud (Say Health<100)
Set HUD to 10