In targeting a hit rating, bear in mind both your talents and those of fellow raid members. Balance druids' Balance of Power adds 4% hit chance for themselves. Elemental shamans' Totem of Wrath adds 3% hit chance (and 3% crit) for all party members. The Draenei racial ability Inspiring Presence adds 1% hit chance for all party members. A well constructed raid group may have a party a balance druid, an elemental shaman, and either 3 mages or 2 mages and a shadow priest.
If you are the druid in such a group, your hit rating cap is 113 if Horde, 101 with a Draenei shaman. This is very easily reached in endgame gear without gemming or enchanting for it.
Additionally, that hit rating is only useful against raid bosses. Against raid trash and everything in 5-player dungeons, most of it will be wasted. (Probably *all of it* on items will be superfluous, and, if you happen to be a druid grouped with an Elemental shaman, some of the talents, too). If you have multiple generally viable trinket options, some with hit rating and some with crit (e.g.
Scyer's Bloodgem and
Xi'ri's Gift), use the latter most of the time and the former for raid boss fights. Consider distinguishing between raid boss gear and "everything else" gear in other slots, too. To whatever extent having totally separate sets is impractical, as well as when your available options deep in endgame far surpass items like Xi'ri's Gift, just go with whatever works best for the bottleneck obstacles, which almost certainly means boss fights.
Other than this, there are no definite numbers "to aim for". When you have gear options before you, maximize both spell damage and crit rating, which are, itemization point-wise, of roughly equal value to a Balance Druid.
Mana regeneration is very tough to analyze in a vacuum. If your group includes a shadow priest, you will probably do fine targeting damage and crit chance and simply taking however much m/5 you happen to get. If not ... I can't speak from experience raiding endgame content as a moonkin. Bring multiple stacks of mana potions in any case, and be prepared to use them as often as possible on tough boss fights in addition to whatever other mana regeneration is available. Many raid boss fights last up to 10 minutes before the boss enrages. Some have no enrage timer and are even longer. I know playing a (frost at the moment) mage in some raid fights I keep Mage Armor on and use 4 mana gems, Evocation, and 3 or 4 potions in encounters where I'm basically chain casting Frostbolts for 10 minutes straight. Balance druids don't have gems or Evocation but do have more constant mana regeneration talents and the ability to whack things for mana. In many boss fights doing so is perfectly viable when you need. Perhaps Setai or others could speak about how their mana pools hold up on various fights.