How are they broken though? It's only a speed boost. Sandstorm doesn't increase the power of a certain move type, and all chlorophyll users are all grass type.
The problem with Drizzle+Swift Swim was that the Pokemon getting the speed boosts were water type, therefore also getting their water stab moves boosted by the rain.
You can get around chlorophyll/sand rush with priority.
To add on to this, let's look at the two main abusers.
Doryuuzu / Excadrill
Venusaur
Venusaur's rather crappy typing leads it to have several things that can counter it since almost all run Sub, Synthesis, Sleep Powder, or Growth in the first two slots, while the last two slots are either HP Fire / Sludge Bomb
, HP Fire / Giga Drain (or Energy Ball, Solar Beam, etc.)
, or Sludge Bomb / Grass STAB. Sludge Bomb + Grass STAB is quite easily walled by Nattorei / Ferrothorn and Skarmory, while you would have to deal with the (omg innacurate) sleep powder. HP Fire+Grass STAB is more complicated, but Heatran and Shanderaa / Chandelure can survive and KO, unless you managed to let them get to +3 or so. Grass STAB + Sludge Bomb is rather shoddy coverage wise, while being counterd by, again, Nattorei / Ferrothorn, Skarmory, and even Heatran again. Needless to say, Venusaur is subject to meh-ish typing, innacurate set up assists, and 4 slot move syndrome. Venusaur is still a very nice pokemon, but unless you can manage to gain the set-up, you tend to have a difficult time with him.
Doryuuzu / Excadrill is almostthe same. He has decent coverage, but has some solid counters. An Impish 252 HP / 252 Def (which is pretty standard and the best option) Gliscor can easily take any of Dory's moves while being able to KO with EQ. Sure, Return would provide some issues, but then Excadrill is screwed coverage wise while most carry either X-Scissor or Brick Break in the 4th slot. Skarmory works the same where he can shrug of and resist, while also having the wonderful ability to phaze Dory out. As you can see, most Sand Rush and Chlorophyll users you've seen in the metagame since Fall are quite good, but have no way of being broken. Powerful? Of course. Counterable? Absolutely.
Ah, but what about Swift Swim? With a core of Kingdra / Kabutops / Ludicolo, all of which had double the speed, great offensive stats, and a horrifying 50% boosted Hydro Pump / Surf / Waterfall, a Swift Swim abuser could easily win a game with little to no trouble at all. Since the three were so common and uncounterable as a group, but they themselves weren't broken outside of Rain, we had to ban Drizzle+SS.
Edit: At post above.
Wow, I was *%#&$# crazy that night when I posted that. Well, needless to say, if we're talking Special Sweepers, both are good in that regard, but have huge differences that make them uncomparable. I'm sorry for not realizing this earlier. Truly so.