Unless every time you die you get an ace and the rest of your team survives with enough health to immediately push or get dragon or baron- unless you can absolutely guarantee that outcome, you should avoid dying at all costs.
deaths generate gold and xp for the enemy team. If you initiate a teamfight and then die, no matter who wins the trade, one person killed you and four assisted. That's about the equivalent of 10 and 6 cs respectively, basically for free.
That being said, your kdr as a tank/init is expected to be a little more gnarly than the others at let levels. But smart players will ignore the tank and attack the carries, then you after, do you shouldn't be the one dying THAT OFTEN either. With amumu your init is to flash in with w on, r>e, and then q the squishiest person you can hit. After that if you're team is smart you can scurry off while they peel enemies off of you and your carries, our while the event is dazed by amumu's sick init :)