Projectiles should pierce 5+ targets
Only if we agree to remove melee cleave limit of three and bring it up to unlimited targets.
Right now, all piercing projectiles can only pierce 5 targets.
That makes them not better than AoE attacks.
I’m not sure what you mean by that. AoE skills also only go up to a maximum of 5 targets per strike and can be blocked or negated through invulnerability.
Pierce should be as on par to AoE skills as possible, so increasing the cap might make pierce skills too powerful, particularly in WvW large zergs or similar content that can have several enemies clumped together.
Therefore, I think pierce skills are fine where they are.
An AoE has to be blocked by each player individually. A projectile has only to be blocked once.
AoE’s have a higher chance of hitting players, since they cover more ground. It is currently way more effective to just use AoE than to line up your projectiles.