should be built by someone on your team every game. This may seem like a no-brainer, but people sometimes don't. The fact is, this item benefits your team way too much to be ignored. If all of your team is slightly damaged including you, this will heal a total of 100 health every ten seconds for your team. That's 600 extra hp for your team per minute (because, no one is ever hardly at max hp for long in arams)! Magic damage is everywhere in ARAMs, so the MR aura really helps out too. The item itself gives the person who builds it very good defensive stats as well. Don't ignore it!
"OH NO! Our team has twos due to communitcation errors!" What would you do in this situation? Don't sweat. You have the option to double up the health regen aura, the aura is differently named, meaning you can have two going on (Potential heal of 1200 hp every minute for you team?!). Although doesn't really synergize with many champions, and in general isn't as useful as Bulwark, it will help you siege towers a bit faster. The promote active is kind of a moot point, you don't get to use it often, it's not very useful either. As far as cost effenciency goes, it is if you are by one champion, but finding a champion to benefit from all of the stats it has is the tricky part. It's better than selling the emblem and being out gold if you can benefit from all it gives though... (If you go to the item page it has champions whos pets get special "benefits" from it... ;) )