Graves top is meta - Due to his very short range he actually has trouble in bot, getting harassed easily. However in top where there's usually melee champions, he can hit all his pellets giving large lane dominance. True grit also makes him a lot more tanky than your standard marksman. He doesn't play anything like the old graves, and is now far more a bruiser than a marksman
Varus mid is meta - Varus has always been a caster marksman (similar to Ezreal, who is also fine mid). Mid is actually great for Varus due to the shorter lane helping with his low mobility. You're basically getting and AD poke from mid instead of an AP poke from mid (something like Corki, another marksman that works great mid)
Sivir bot - uhhh, not sure why you pointed this one out, but yea, works here. So far your team is far too AD heavy, but if any ADC is going into this comp sivir is actually the best possible pick. Her ult will help Varus with his low mobility, and help Graves stick onto people with his low range.
Picking up Rammus was certainly something you wanted to do with this comp, at least it denied that from the enemy. Each of these picks you pointed out is perfectly acceptable individually, it's just as a comp it's a bit overwhelming with AD damage. Which wouldn't have been any different was it a Riven top, and Zed mid.
As for babysitting them, Only Varus really needs any babysitting. Graves can handle himself as well as any top laner. If he gets too aggressive and dies, wouldn't have been any different with any other champion. And if you had some other low mobility mid that fit into your "acceptable not marksman midlaners" such as Cass, or Kass, they would need just as much babysitting.
