Beggar-
We agree and dissagree.
There are other things that a cleric -must- do, RP wise, in order to be a cleric. One is preach and teach about their God and the dogma, the other is to actively promote the dogma in life. (ie, teach it and live it) These activities define what a cleric is at it's core, and though perhaps performed in different ways for different dieties. (Cyric, Mask, Shar--clerics are not exempted from these.)
With this, I absolutely agree to the highest possible extent. Any Cleric who does not do these things is not serving their deity. In fact, I would stretch this beyond even a cleric to encompass other divine magic users. The god's don't grant magic to individuals for nothing in return. There is always a price to pay, and that price is service to the deity granting the powers, and bringing others into that deity's faith.
For any other cleric to seek out blessings from another God or a cleric of another God is an indication that you do not trust in the powers of your own diety any longer to take care of you, or the problem at hand.
That in my opinion is incorrect. Everyone is aware that deities have a sphere of influence - a focus - portfolios in which they control and rule over. Therefore, it is perfectly reasonable for a cleric to make a
token offering to another deity, Umberlee for example, when they know they are going to go on an exceptionally dangerous sea voyage.
That does not translate into a crisis of faith. That doesn't mean that suddenly the Cleric is wavering in any way. It simply means that the cleric is acknowledging other deities exist and have power in Toril. Torm can't save you while on the ocean but Umberlee can. Giving a token offering to Umberlee can ensure that she doesn't send a massive wave to crush you and your ship, drowning everyone onboard.
There are exceptions to this, of course, such as Bane and Cyric. Their dogmas clearly state that they are the only deities worthy of worship. Worshiping another deity would be considered a sin in those faiths, but it is not always so in others. Of course, there are also those who take things to an extreme, refusing to give worship to any other deity but their patron however, they are exceedingly rare and have often developed heretical beliefs about their own faith.
This doesn't mean you can't work with other clerics, though relations would likely be strained. Why would you want another cleric to edge in on your territory, and try to convert the people you are trying to convert? What?! He cast cure serious and saved his life...and is now preaching about how great Waukeen is! I've got to stop that...I'll show them a -real- miracle.
Certainly a Cleric would feel threatened to some degree if another priest is trying to convert people right in front of him. As long as their general beliefs are not directly opposed though, at worst, it would be considered rather rude. However, that doesn't mean that every cleric is out there playing a game of "my deity is better and bigger than yours" contest. However, even in this case there are exceptions.
Let's step away from the Faerunian Pantheon, because they are loosely aligned and more egomaniacal than deities of other pantheons. Let's look at the Elvish Pantheon instead.
The Elven deities are bound together in a tight pantheon, with a clear defined ruler - Corellon Larethian. An Elven Cleric of Labelas Enoreth, while primarily praising him as his patron deity, would still offer - perhaps even frequently offer - praise to other Elven deities such as Corellon. It would be unnatural for them to do anything else.
This may even be truer for pantheons such as the Mulhorandi that are smaller and perhaps even tighter than the Elven Pantheon. Horus-Re is the undisputed ruler of that pantheon and is likely given praise by every single worshiper of every other god (with two exceptions) of the Mulhorandi pantheon. I can guarantee you with 100% certainty that a Cleric of Isis is still offering prayers, perhaps even frequently to one or more (perhaps the entire) Mulhorandi Pantheon, and specifically Horus-Re.
This is less true for the Faerunian Pantheon because they are a loose pantheon. However, unless otherwise stated and where common sense applies (something any Cleric should have an abundance of) they are still offering prayers to more than one deity. Perhaps not as frequently as in a tight pantheon, and much more likely to be less earnest than someone who prays to the Mulhorandi Pantheon, but still common enough to be worthy of notice and mention.
You simply cannot apply monotheistic ideals ("My god will get angry at me if I pray to another god...") to the deities of Toril, unless the deity has stated clearly that praying to another deity is a sin. It is a sin for a Sharran to give praise to a good aligned deity. It is a sin for a Banite or a Cyristist to give praise to any other deity but their patron. These are exceptions, not the rule, on how faith and belief is generated on Toril. Unless there is a cannon change on EfU that I am unaware - in which case it should be clearly stated in Information for New Players - this is how it works.