imo there needs to be some middle ground. I like the idea of having an icon above it like UT2014 has done, but I don't think showing seconds is the solution. There should be some kind of advantage to the player who picked up the item.
I think there should be colors, or 5-10 second intervals. So if something respawns in 30 seconds, red means it has 20+ seconds for resspawn, yellow is 10+ seconds, and green is under 10 seconds. that way the player who picked it up can time it and have the advantage, and the other player will have some assistance in knowing when it respawns, but not the luxury of knowing when it exactly respawns.
Wtf? The player picking it up already has advantages. He gets boost in armor or HP and he does not need to figure out what exact second the item was taken, as its printed on their screen. That is enough advantages, so why would you add weird new advantages? Showing seconds is intuitive.