They aren't claiming that DGC, DOGE, LTC, or any of the "main" coins are merged. Only HUC, ORG, PTC, and USC are claimed as merged. USC and HUC at least are designed to be merge-mined. Don't know about the others without looking.

Nevertheless, this looks very scammy.

72 hours' test (which should be enough to sort out variance even if this is running p2pool underneath) at ~50Kh/s yielded:

DGC   0.34859148 vs ~5 elsewhere
DOGE   60.78225803 vs ~650    
LTC   0.00426753   vs ~0.04    
42   0.00000050   vs
CAT   0.03166796   vs 1
HUC   0 vs
PTC   0.94306607 vs    
ORG   0 vs    
POT   0 vs
USC   0.09437904 vs

The total of all that is about 0.00013645 BTC per day total for all coins and being very generous about a guesstimate at the value of USC.

That's about 9¢ per day for 50Kh/s. Coinwarz says 50Kh/s would yield 11¢/day on Catcoin, 32¢/day for 42, 22¢/day for LTC, 27¢/day for DOGE, or 14¢/day for DGC.

Bottom line: you'll get more value out of straight-up mining Catcoin, the worst performer of the bunch.

Maybe not a scam, maybe just incompetent.

I lost about 70¢ running this test. Hopefully it will save others the time of repeating the mistake with real hashpower.