Grotesques/grotesqurie question

So I've been reading the last big assault troop analysis page. I keep seeing that grotesques re roll to wound vs T4 or less. Am I missing something? I'm not complaining it would be awesome I'm just confused on how. If someone could explain I'd really appreciate it thanks!

They have poison weapons. The poison special rule says that if you would wound on a better number than your poison, poison instead let's you reroll to wound. So, since S5 grotesques would normally wound T4 on a 3+ instead of a 4+, they wound T4 on a 3+ with a reroll to wound.

Oh thanks man! That's pretty darn good !

Technically the trigger to re-roll is Strength > Toughness, rather than a lower roll being needed, but in effect BetrayTheWorld is right for Grotesques.

If Grotesques were to get a 2+ poison weapon in a future upgrade, they would still get rerolls vs Marines, which would be amusing.

This makes me wonder: If i roll Shred on the Latest Experiments, can i re-roll to wound twice?
Once for Poisoned and once for Shred? Or does "No single dice can be re-rolled more than once" still count, even though it's 2 different special rules?

Edit: Would make shred rather useless when there are only enemies with toughness below 5 on the table.

It makes shred rather useless, since you may only re-roll a dice once.

Shred wouldn't be useless against T5 and higher though

And given the prevalence of bikespam, It's likely you won't be getting rerolls against marine armies unless your experiment is +1 to str or shred.