This is fairly simple and should be well supported if your environment is as they describe. I do think there's a mistake in their documentation though, their talk of ad name@domain is unhelpful. You bind to AD / domain controllers using the format I describe below. You'd identify users within AD (e.g. specifying a user to connect with to carry out your LDAP query) using the format firstname.lastname@example.org
When carrying out LDAP queries, rather than binding to a specific Active Directory server, it's possible to bind to the address of the AD domain itself.
This should load-balance queries as they say, as well as providing an element of resilience in the OTRS service if you have an AD server offline for maintenance (e.g. it will only connect to available servers).
For example, lets say you have a domain, ad.example.com with two domain controllers, dc1.ad.example.com and dc2.ad.example.com. You can connect directly to either domain controller with your LDAP bind statement, e.g. you can connect to dc1.ad.example.com. It should also be possible to bind to ad.example.com rather than to a specific server.