How do we feel about Zilean's Chronoshift?

Is it balanced as it is now, or are there certain tweaks we could come up with to make it a much more 'risky yet rewarding' ability to pull off?

On a 3 minute cooldown ( It NEVER feels that way, feels like it's always up ) and on a 125/150/175 mana cost throughout the ranks, this ability returns an ally or themselves to life at full health after a certain period. I know the answer here is to 'Bait it' or 'get good' to most people, but it really feels like this ability causes an already losing battle to grow even worse at the push of a button. Any efforts to catch someone can be nullified, any Assassin you burn is restored to life in just a few seconds, and so on. What I want to ask GD, from unranked to challenger, do you find the costs to this ultimate fair or should there be a rework to make it more risky to use?

By risk I'm talking something along the lines of reducing the 7 second timer it remains on an ally by maybe a couple seconds and reducing the amount of health it restores depending on how fast the affected ally takes to die. If we look at Soraka, well the old one anyway, her heals were entirely dependent on being 'clutch' to get the most bang for the mana cost. She was the dedicated healer who excelled at keeping people alive, but could never raise them from the dead at the cast of a button. Would it be too much to ask that Zilean be considered for a new mechanic that makes it so his ult requires better timing to be used based on current health? For instance, it's not a skillshot, it's a simple press of a button that guarantees whomever dies is brought back within several seconds. What if we kept that, but made it so the amount of health the ally had before it went off is reduced when brought back by half, and if the ability is used at a clutch time period where they're at half health or less and they get killed, they've revived back at full health?

I know there will be some people out there who feel the change is not necessary, that Zilean is balanced and that all it takes is some skill to put him down. I did lose to a Zilean in a recent game, and the entire enemy team played very well, but it was the rate the ultimate came up and the simplicity to use it that bothered me. There never felt like there was much heavy decision making on where to use it during the game and whenever we were jumped and managed to get one of them, while significantly behind mind you, Zilean nullified any mistake made in the engage and they were free to resume again. Does anyone feel like Zilean's ult should be used much more preciously rather than carelessly, a push of the button move that erases the mistakes a player makes in a fight?

Comment with your opinions on why Zilean's ult is fine the way it is regardless of lane, or why a rework to his ult or maybe his kit to work around his ult would be a great idea!