If the shield protected from all damage, which it would if it protected against splash damage, lasers and disks, you could have 2 gohans who are invincible. One puts a shield up, when he is almost out of ki the other puts his shield up and the first recharges and then when the second it almost out of ki the first puts the shield up and the second recharges and so on.
I think disks and lasers should get through and so should high power level attacks but it really should protect against splash damage since any good player will just shoot next to the shield making it useless.