First of all Jack this thread is from almost 2 months ago, and the other 2 threads you revived were from even longer. It's usually good practice not to revive threads older than 1 month unless there's a good reason (or the forum is very slow).
Anyway in case it's still useful I'll throw in my 2 cents.
Burning Metal and Music of Life are your best friends, and with those 2 songs your life is complete. In my opinion the Music of Life Talent is always worthwhile, but the Heavy Metal talent is only useful if you plan to solo and solo a lot. I've never regretted Heavy Metal, but "wasting" 15 points in order to unlock it is rough.
As Jack said, for soloing you need increased movement speed. Getting up to 30% is relatively easy by the time you're at Venin and should be done. (cast speed is useful too for recasting MoL either in the field or before you start circling in Venin). As for Certificates, don't worry about anything with offensive attributes. The only certs you need are Cast speed or defensive ones (Agi, Evade, Def, HP, Ele Res, etc.)
Rarely in large 5-8man dungeons is a bard spamming cure, and thus should have plenty of time to keep up buffs. Bards should always keep Music of Life, Spirited Melody and Songs of Illusion up. There's never a reason not to and are all incredibly useful. Actually because these are a Bard's main 3 songs, I would suggest the MoL talent and the SoI talent (minimum 5 points).
The Spirited Melody talent is similar to Heavy Metal in that you have to essentially waste 15 points in order to add to it. It is possible to have 5 points in SoI and Spirited Melody talents while also having Heavy Metal, so the choice is up to you. Speaking of which casting Burning Metal while in dungeons is useful, just make sure to wait for the tank to have aggro.
Other songs like Demonic Symphony, War Rhyme or Holy Concerto are useful on occasion, but if you don't have an Illusionist to maintain your MP (and boost your cast speed) I'd leave them out. If you have the cast speed and unlimited MP supply, you may as well include whichever are most useful, depending on the circumstance.
I'm taking this to mean 3-man dungeons healing as a bard.
In my experience, 3-man dungeons as a bard consist of casting Music of Life, Songs of Illusion and spamming Cure on the tank. If you have time, Spirited Melody is incredibly useful but survival before offense in most cases.