I haven't played a Cleric dualled to a Ranger, but I have rolled one up before. It looks like a viable character to me.
I don't know for certain, but I suspect that the casting level will be determined by the Ranger's level. If that's the case, then because of the rate of advancement, a Cleric dualled to a Ranger would have a spellcasting advantage compared to a multi-class Cleric/Ranger (which gains levels more slowly) and a slight disadvantage compared to a Ranger dualled to a Cleric (which gains levels faster).
However, there is one thing to keep in mind. Rangers can only learn up to 3rd Level spells. Therefore, if you want to cast 7th Level Cleric/Druid spells, you need to advance your Cleric to 14th Level or higher before dualling to a Ranger. This will require 3,450,00 experience points (1,350,000 + 2,100,000).
Let's say you advance your Cleric to 14th Level. At that point, all of the Cleric spells for a Good-aligned character will appear in your spellbook. When you dual to a Ranger, your spellbook will appear to be wiped clean. Starting at 8th Level, you will gain the ability to cast Druid spells like any other Ranger (including up to 3rd Level spells). When you reach 15th Level Ranger and regain your Cleric abilities, your spellbook will suddenly contain
every Priest spell available, including Druid as well as Cleric spells, except for those that cannot be used by a Good character.
When you advance to 18th Level Ranger (which requires 1,350,000 + 3,000,000 experience points), you'll begin acquiring the High Level Abilities that are available to Rangers, including Power Attack, Whirlwind Attack, etc., as well as the cheesy favorite, Deathblow, which does, uh, interesting things when combined with a spell like Fire Seeds.

(Thanks, UserUnfriendly.)
Some players would rather have Cleric High Level Abilities instead of Ranger High Level Abilities, but that's a matter of personal taste. The only disadvantage that I see in a Cleric dualled to a Ranger is that you have the Hit Points of a Cleric. (There's no benefit in having Constitution over 16.) On the other hand, a character with Ironskins and Hardiness doesn't really need to be a Hit Point factory.

You also have to wait a long time before you can cast 7th Level Druid spells, but that's just the way it is when you play a dual-classed or multi-classed character. If you want Cleric High Level Abilities, more Hit Points, and the ability to cast high level Cleric spells a little bit earlier in the game, then you should consider the natural alternatives, a Ranger dualled to a Cleric or a multi-class Cleric/Ranger. Any of them make fine characters.