Unfortunately I cannot perfectly answer your question as my paladin is only level 62. However, he is single-trained in spiritual lore.

I had a summoning-heavy build last year, which was 40 summoning, around 10 blessing, and at least one religion.

Before the new fixskill this May I burned an old one and went for 40 religion, 11 summoning, and 10 blessing.

Lots of people seem to love and promote blessing lore, so I figured I'd give myself a shot at the others.

Requirements: I always want >= 9 summoning to infuse Divine Strike into my bonded weapon. I also always want Consecrate to give 2x the number of blessings.

While I enjoyed being able to return myself with 1620 at 40 summoning lore, it didn't come up that often, and was just as often to lead to a funny and confusing situation for people rescuing me than something useful. Though I still love the idea of this skill. Having 16% more DF with 1605 and tons of mana on 1625 was a pretty noticeable boon.

Since my paladin is nearing the end of RR hunting, I wanted to maximize his ability to raise the dead, hence the religious lore. He also hunts most of the Citadel with 1617 active (the +8 benefit is nice), and the "(Paladin) of (Deity)" title is a pretty nice flash.

I'm also curious about your question. I think at lower levels it makes a lot of sense to push one lore ahead for some of the mid-range benefits. However, I expect as my paladin increases in training, eventually I would diversify, unless I found myself regularly using all my raises per day (unlikely, there are several cleric alts around RR mainly focused on raising, so half the time I can't even get in the raise even if I do the rescue).

For me, in terms of training post cap, lores are absolutely a fantastic value even at the 2x cost. There are several lore benefits for paladins that work as multipliers to our other training and not flat additions, which is far more powerful. They are arguably good enough in terms of the AS/DS and other flat bonuses. But, the DF multiplier from 1605/summoning lore and the more targets for 1630/summoning lore are significant contributers to killing power.

I am currently at 100 ranks in summoning (77 blessing, 25 religion) and I am not fully convinced that I shouldn't be at 150/27/25). Only the relatively high bonus per rank of the early blessing ranks and the kneeling effect from religion stop me from dumping every single point into summoning at something like 200/2/0.

Sweet is the sound of the pouring rain,
And the stream that falls from the hill to plain.
Better than rain or rippling brook,
Is a mug of beer inside this Took.

100's circle is way way harder to ward things with. It has to be balanced to deal with 3x spell learning sorcerers and the paladin circle only is balanced against the more like 1x training paladins.

Sweet is the sound of the pouring rain,
And the stream that falls from the hill to plain.
Better than rain or rippling brook,
Is a mug of beer inside this Took.