Should we create another domain for a Storage Array in Remote Site ?

For answer to your question I need first to clarify what is a domain and the difference between multi domain and single domain .
Navisphere Manager lets you create storage system domains and
multi-domain environments. A domain lets you manage and monitor
a group of storage systems using a single instance of Navisphere
Manager and a single login; a multi-domain environment lets you
manage and monitor a group of domains (potentially all the storage
systems in your storage enterprise).

All storage systems within a domain must be running the storage
management server software, and must be connected to the network.
Each storage system can belong to only one domain, but a domain
can belong to more than one multi-domain environment.
Each domain has a master node (master storage system) that maintains the
master copy of the domain data - the storage systems and global user
accounts that make up the domain.
All domain and global/account information is duplicated on all systems in the domain, so if a system fails, the information is retained and other systems in the domain remain accessible.
If the system that fails is the master node, no global updates are allowed until you choose a new master or the failed system is replaced.
The multi-domain feature lets you use the same instance of
Navisphere Manager to manage and monitor any or all storage systems in the storage enterprise, even if they are in separate domains. A multi-domain environment consists of a local domain (domain from which you will manage and monitor all other domains), and gateway domains (domains managed by the
local domain).
The multi-domain feature allows domains that may be
geographically dispersed, but are part of your storage enterprise, to
be managed and monitored by one administrator ¿ providing a more cohesive view of the enterprise. This feature also offers the
option of a single-sign-on user account ¿ letting you log in to the
entire multi-domain environment using one set of security
credentials as long as each domain within the environment has
matching credentials.

In your specific environment because you use only two array probably is better to configure a single domain .
In case you will lose one array you can still access the second clariion with the same security credential .

And when the other storage will came up it will automatic rejoin in the domain and the security information will be propagate again from the surviving array (if surviving is the master ).
You can change the role of master in the domain online with out any interruption also if the other storage is down you can elect the surviving storage Master of the domain
Regards