Quoting: Ledge_And_Dairy
This exact trade was proposed on HFboards by another flames fan and LA fans were calling it an overpayment. It was proposed because LA likely does have plans to move Campbell (assuming quick cant be moved) and they asked about any available young defense with NHL potential. Outside of Bjornfot and Clague LA really doesnt have any future LD down the pipeline and under the circumstance that they dont project for top line picking up a young LD that shows top 4 potential and is NHL ready is at the minimum a great insurance and at best really solid depth.
Im not exactly disagreeing with your POV and the whole overpaying for a in conference trade. LA doesnt really see Toffoli as part of their future and likely dont have to worry as much about him 4 years down the road when their young guys start developing.
You left off Mikey Anderson, who is a top quality two-way defensive prospect that has a better chance of succeeding in the NHL than Kale Clague. I would project him to be the 2LD of the future for LA, with Clague rounding out the bottom pairing. If you were to say that the Kings had a hole at RHD, then I'd perhaps agree with you, as it is unclear if Durzi will ever become a NHL-caliber player, and whether Walker and Roy are capable at filling the 2RD/3RD slots on a playoff contender. They're doing admirably well on a poor team, but unless they can both take solid steps forward next season, they're going to have to upgrade there. However, LHD is probably the only position where the Kings have sufficient depth. They won't move their best trade chip to add another LHD prospect.
I also disagree that LA has plans to move Campbell. I fully expect LA to carry three NHL goaltenders next season into the expansion draft. One of the Kings glaring prospect holes right now is at goaltender, as they have Cal Petersen who becomes waiver eligible next season and will be in the NHL, and Ingham and Parik, who are 20 and 18, respectively, and both need several more years of development before either is NHL ready. The other two guys in the pipeline, Villalta and Kehler, do not look as if they will be NHL-quality goaltenders. If the Kings trade one of Campbell or Quick and the other is taken by Seattle in the expansion draft, the Kings will be in a really tough spot with no one capable of backing up Petersen for two seasons or so. If someone wants to give up a quality haul for Campbell or Quick, then I can see the Kings moving one of them, but they're not going to move Campbell just because they're not able to move Quick. If after the expansion draft, the Kings still have both Campbell and Quick in the system (e.g. Seattle selects Roy), then I can see the Kings trading Campbell for whatever they can get. Until then, they're not interested in moving him.