I'd say that Sand weakens anyone weak to Sand's main sweepers significantly - those vulnerable to Doryuuzu for example. The team choice is wider because mostly of the 3 types able to abuse Sand to some extent (excluding Cacturne), whereas the other weathers have one or two (Sun).The fact that scarf toed started to get popular is clearly show how dory affect the metagame. Also unlike rain and sun sandstorm doesnt particularly weaken any particular pokemon so your team choice is totaly wider than sun and rain. I always hestitating to use Kurimugan in Ran for example(kurimugan trolling FTW) thats why Sand has an edge in term of
weather advantage.
I run a Sun team and the same applies - even with an opposing weather to counter it Doryuuzu manages to beat me occasionally, though not half the time. However I would say that the times it does is down not to Doryuuzu itself but my opponent's ability to keep their weather setter alive longer than Ninetales, as my entire team pretty much hard counters it out of Sand. Similarly, the Ground Genie can pose similar issues if their weather setter stays alive long enough. So to me, it doesn't seem too overpowering.You must be ranked really low if you aren't facing teams with Mole because I just faced 10 Sandstorm teams in a row running Mole on the ladder. I have MP Roobu and other stuff to deal with it and it still gets me half the time. And that's without getting SD off, if it does get SD off then the game is over. Unless you want to make a team of 6 Pokemon that counter Mole (which would be a bad team) then it's going to wreck you from time to time.
However, the fact that I don't have issues with it too often may be down to the fact that my team is a Sun one is reasonably concealed until I bring out Ninetales, and that Hippo in particular is commonly a lead. This enables me to pick it off (which my team is somewhat specialised to do due to its nature) then completely eliminate the threat of Doryuuzu by setting up Sun.