Spot on.
The only way this situation resolves itself without the expenditure of major assets is to have one of Pettersson, POJ, Rutta, or Smith play at a replacement level that allows you to trade Dumo for their replacement. You don't trade Dumo to replace Dumo. You trade Dumo for Pettersson's replacement...who replaced Dumo.
We aren't far enough into the season yet to assess this. I'd advocate for Soucy or someone similar. Likely in a Dumo for assets, assets for Soucy type three way.
To HSL's point though, Sullivan needs to do a better job at managing minutes. You can't run Dumo-Letang 25 min a game. If you really, REALLY have to shelter the bottom pairing THAT much, then we have the wrong bottom pairing. f*** it, waive POJ and bring Smith in. Make a trade for a better bottom pairing guy. Switch the pairing up.
Pettersson-Letang
Rutta-Petry
Dumoulin-Smith/POJ
This is where Sullivan needs to be the bigger man and say "Hey guys, something isn't working. Let's discuss it" rather than "if we just keep doing the same thing, eventually it will work itself out". That's a Dan f***ing Bylsma approach and all it does is ruin seasons.