[caliaca]

The fact is in PvE status effect should last longer. It literally only breaks when you try to do PvP which is highly debatable rather or not SL2 was designed around PvP and not PvE content but like what's Elite Engine?

A weaker modifier to excel charges, from a potential on the original line of excel weapons, caps the damage boost to around level 1, but allows you to hold multiple charges.

It's over double level 1. And you can always hold multiple charges. 
Elite Engine makes each charge only add 35% damage instead of 50 but only 1 at a time is removed. 

As an illustrative example. If you have 3 charges and one weapon with excel Engine and one weapon without it, it'd look like this.

Using non elite engine:
All 3 charges are spent and damage is increased by 150. Next turn you get one charge back from conversion gloves and do 50% more on your attack. 

Using elite engine:
You have 3 charges and do 105% damage. Only one charge is removed so you have 2 charges left. You can attack again for 70% more damage or if you wait to next turn you'll have 3 charges again and do 105% once more and go back to 2 charges. 
Elite engine just makes you only use one charge at once. 

Its much better over time especially with an est lestrada making the damage differential highly in favor of elite engine.

Labrys can match its damage but over statistical averages will not. 
Kiss Farewell can match it under passive effect but in 1v1s you can't possibly get it except vs ghosts and summoners