True tanking on a Minstrel is not possible unless you're "tanking" against underlevel players in an underlevel instance.
BPE - Minstrels have truly abysmal block, parry, and evade now. (I miss my old passives so very much!)
Light Armor - The changes with ROI to mitigation really do matter. Wearing light armor makes us very susceptible to damage as our mitigation cap is only 40%. For comparison, the mitigation cap for heavies is 70%.
Threat - We have nothing that can increase our threat anymore (the bug with threat decreasers making Song of Soothing a force-taunt is apparently gone). In fact, all we have are abilities and passives that DROP threat. It's on our instruments, books, and weapons.
Damage - With some wicked early spike damage, you may be able to "DPS-tank" for a few seconds. Doing Limlight Dailies, I can even maintain aggro against certain DPS classes for a bit... but only if the RNG has me critting a lot and them not at all.
Healing - Our ability to self-heal and group-heal is probably our biggest asset if you want to "tank." Minstrels are very well-suited to kite-tanking. Drop some healing bombs on the group focusing on the boss, then start kiting the adds in circles while healing yourself. Wardens and Captains can also do this very well, too, so it's not a unique niche for us, but still. As it is, I wouldn't exactly call this "tanking" as you are not actually holding aggro against other players if they're not hitting what is after you.
To answer your questions... no, Minstrels cannot really build for tanking. They CAN tank in some few cases, true, but it's not going to be a regular thing. If you really want to tank, might I suggest rolling a tanking class?
Narlinde, level 85 Minstrel, Rank 10, Member of Trucido ~ Windfola
I've tanked an on-level t1 Tuck 12 man. Holding aggro on a specific single target is close to impossible without other dps classes being careful though. Which is pretty much the problem with minitanking.
The only way I can see this being done is to do so much self healing that all the mobs go after you and you manage to keep your self alive with the healing.
With any number of mobs on you you won't be getting inductions off very well. Then there's the fact that there's so many legacies, traits, skills, etc., that decrease the threat of our heals. We have lowish mitigations, and lowish health(compared to an actual tank), and no amount of healing makes up for being one-shotted. Sure, with a top notch group and liberal cooldown use, a mini could tank a pull, but a mini tanking is going to be the same thing as when a healing mini gets a lot of unwanted aggro - chaos. Which could be fun.