In overcharge mode, shield is invulnerable which means it can't be destroyed but i can show you that a riker heavy can destroy your overcharge shield in just 2 hits

Video Proof -

https://youtu.be/ELK7iT17r-8

4 piece true patriot and btsu gloves to proc overcharge, in 1st encounter, as i proc overcharge, my shield was at full health and many npc were shooting at me but my shield got destoryed in 2 hits by riker heavy nail gun in overcharge mode (btsu gloves icon is visible) if you see clearly or in slow motion....

in 2nd encounter, i did same thing but this time my shield dont lose any health because he was not shooting.....even i got my armor destroyed by explosion but shield health don't drop..

This thing have happened many times making shield useless to riker heavy as they can destroy your shield in just 2 hits..

i even tried this with bulwark shield shield but same thing happened where i assume that no matter how much health your shield have, he will always destroy it in 2 hit from his nail gun as he deals percentage based damage to shield like 50% damage in 1 on shield (health don't matter)

I hope massive looks into this and fix this broken mechanic....