The topic is subject as lot of topics are and everyone can have a different preference for sure 
But let us talk some numbers based on a Chest run that really hurts - Tacas Demise - these Dwarven rangers are true killers.
So let's say there are 2-3 rangers in a mob groub u wanna pass. Each fires 3 shots on you for a total of 6-9 shots. Now we have 400max HP and an 10vsDwarves - 2wE shield
6-9 x - 2 Mod = 12=18 reduced dmg. AND u have only 200 max hp when shroud triggers.
And they really hit for a lot. Like 50-80 for sure with a skill even with piercing insignias. So the blocking of shroud is 75% dmg Block chance wich will lead to 100% dmg reduce. That is what keeps you alive a - 2 Mod will not change that.
With a 45HP Shield u can basicly eat 1 Hit for free assuming it's. A ~50 Dmg hit. And ur shroud will trigger with a higher max HP Wich makes u less spike able. Cause shroud (wich is ur life saver, not a - 2 Mod) will be there for you earlier.
Also note that On PvP/GvG when u get spiked u pull a 10vsXX/+HP Shields
And not -2/10vsXX Shields.
-2wE will be better if u receive a lot of hits like a tank that pulls huge groups receiving Basicly 💯hits and more.
As a chest RUNNER 🏃 you should do what the name suggest you - do it like FOREST - and run btch ruuuuuuun.

Run and Take max 10 Ranger hits and your - 2Mod will stay inferior to a +22HP on shroud and a 45HP max mod. Quick maffs.
After the 11+ Physical DMG Hit I agree on the - 2wE mod will be superior* -
still keep in mind it only triggers on Physical dmg so for runs like Hells P. its not really Suited since u face nearly exclusively Fire Dmg. And if u come with the burning titans still keep in mind the 11+ hit rule until the - 2Mod will be better. And if u start tanking 11+ Burning titan hits u rather start running pongmeis 