@HOFB: yes that's coherent with your log, the tank should be the only one healed by the CC BUT as soon as the tank went out of range the CC piked up another unit to heal, that warlock.
I have added more logging to let you better understand if the tank go out of healing range (will spam ERROR tank out he range! and the CC will stop untill back in range, or move herself if want to move to heal is activated)
Pls let me know how it will go after the reset when you will try again with the new release

@ryanmatt: I have never done it myself but to the best of my understanding you have to heal only one target at a time right? well then theese are the steps:
1: go in the config windows
2: go in the Raid menu
3: activate "ignore beacon"
4: activate "select tank from focus"
5: put "healing tank priority" to 100
6: put "multiplier" to 100
7: save
8: in game Keybind your "assign this unit to focus" key
9: manualy put your beacon of light on one tank
10: select the unit you have to heal and put her in focus
11: has the unit you need to heal change select the new unit and make her your new focus
12:?
13

rofit!
Let me know, possibly with a log, how goes for everyone tryng this encounter, pls
@Venus112: he.. if this happen again, pls post the log

Some question: where you using LazyRaider, combatbot or istancebuddy? that's important couse if you where on instancebuddy is a instancebuddy bug, if you where on combat bot it's a CC bug and if you where on lazyraider you should jhust have selected the new tank in the lazy raider config windows

I' happy that for everything else this is working good for you! ^__^