The Rocna is a serious anchor. I still debate using my Fortress in Great Salt Pond. I have had my Rocna ever so slowly drag in some of the thick slimy stuff. I tend to back down hard and this can make it tough to get it up.
We all seem to like what works for us, resulting in a lot of anecdotal evidence in these anchor posts. Unfortunately, there isn't a lot of objective qualification on technique and specific bottom conditions.
I've been going to the Great Salt Pond for over 30 years and have used Danforth high tensile, Fortress, and (primarily) CQR anchors. There I have anchored in various bottom conditions: sand, mixed sand/weed, and gooey mud/weed.
The only time I had a problem with dragging (once in all those years) was when I couldn't get a good set in an area of gooey mud/weed. This was on a busy weekend (first mistake!) when the only area available had such bad holding--otherwise, why was it available? I was up at 1 or 2 AM when my CQR started dragging slowly. There were plenty of other boats dragging at that time and in that vicinity. I was able to move a short distance and get a shaky set in the same area and held for the rest of the night in maybe 20 kts. Based on experience over the years, my Danforth and Fortress backup anchors would likely not have penetrated the weeds, so I never deployed them that night.
For what it's worth that questionable area in the Great Salt Pond in along the north central area of the anchorage and it hasn't gotten any better over the years (I've checked.)
The worst conditions I've encountered many years ago in the Salt Pond was when the winds picked up to 50 mph (per NOAA). My 2500 lb catboat was held by a 6 or 7# danforth high tensile in a sandy patch in shallow water NW of the Sullivan House. Lots of boats dragged that night. The shallow water prevented bigger boats from coming down on our catboat fleet, thankfully, with one grounding to a stop 20 ft upwind of one of our 2' draft boats.
So, if you are trying to anchor in the Great Salt Pond, I'd stay with my CQR as primary, backing down hard to assure a good set. If I can locate a sandy patch in some of the shallower areas, I'd be comfortable with the Danforth high tensile or Fortress if you are expecting high winds. BTW, expect 20 kts in the Great Salt Pond on a good day!
I don't have anything against the "modern" plow style anchors (Rocna, Manson, etc.), but I haven't seen a convincing argument to switch from something that works for me. The recent Fortress-managed test with a muddy bottom reported in Practical Sailor certainly didn't convince me, so I'll stick with my mix of CQR and Danforth styles.