IMO, while you can do a decent tanking/off heal build, it really does require being around 70. Tanking with a prot pally requires 41 points minimum, so don't expect a good tanking/healing build at 60. Even at 70 the most you'd want to put in is 20 into holy.
I mean, you just can't really halfass talent trees with a pally like you can with a warrior (since their 41 pointers suck) because pretty much all the definitive talents for each spec come at 25+ points in, aside from illumination (which is less definitive now than it used to be).
Now if you want a prot build that can still solo... you're still going to need seal of command, but you could go with a reckoning/seal of command build. Right now I'm 20/0/41. Believe me, you may be bored of ret, but soloing as holy is garbage. If you're going to keep soloing and you want to mix it up, get to 61 and then just go 0/41/11. You'll be able to tank and still do decent solo dps, though your soloing style won't change any (still a 2h and seal of command).
edit: just to clarify, in all honesty blizzard's pally design means they can't seriously tank outland instances unless they're 41+ into prot. It's just too hard to get enough threat and mitigation otherwise, although I'm sure improved righteous fury would help a lot. It's not quite like warriors where they still have the core of their threat building skills regardless of talent spec, and mostly get mitigation/rage reduction out of prot. And tanking requires a way different weapon type than soloing/healing. Pally tanking is all about spell damage, so you've gotta get yourself a caster sword/mace to increase your threat output, and then otherwise you just go with the same kind of armor as a warrior.
At the very least, to tank you need holy shield and blessing of sanctuary. With those you build the core of pally tanking, which is blocking and dealing holy damage (which in turn causes more threat). But I would hate to solo without seal of command, personally. I tried it for a month or so with holy, and all I really wound up doing was grinding a few super easy quests, then waiting until groups needed a healer and I went along. I know my experience is not the same as prot, where you at least get reckoning, but blizzard has stratified the pally in such a weird (and IMO dumb) way that it's impossible to be good at two things, but you can be great at one and average at another.