You need the lowest possible Duration on an EV Trinity to make sure you get all or most energy pulses from EV. A slow EV won't use all of its pulses because enemies die too fast - even if you start off with Well of Life.
In addition, a 'fast EV' can be recast quicker and especially later in the game, fast casting becomes essential to keep overshields up at all times. It also allows you to get more overshields stacked in a shorter period of time, it allows the rest of the team to get more energy/sec and thus continue their ability spam at all times.
Range 235% or 190% at the bare minimum is recommended because this will ensure your EV's hit all team mates even if they are a bit out of the way.
Concerning Vampire Leech there is another balancing act going on with EV Trinity - Efficiency versus Power Strength which you balance out by varying Blind Rage ranks. You would think that max efficiency is useless on EV Trinity, but it's not. Overshields on Trinity herself are affected by the amount of energy that needs to refilled after casting EV. A cheaper EV will create larger Overshields per cast. Efficiency at 140% is a sweet spot and balances out nicely as per the screenshot of the Lone Tenno above.
The one thing I would change here is to add Natural Talent for Streamline and take out Blind Rage for Intensify. Faster cast speeds become important especially later as you want to use Well of Life > EV more often. Even a very short Well of Life is a powerful tool to keep that EV going, and it also pulses quicker doing more damage. Ideal to lift up a Gunner and leech it dry. When you do this, you also get to swap out Regeneration for something like Physique to add a nice bit of health pool for the later waves, which in turn increases the usefulness of Well of Life.