Just came across your message when I did a search re this pear tree's fruit setting. My tree is about 8-9 yrs old, and only ONCE did I see a few flowers, followed by about 4 pears. That was maybe 3 years ago.
Because it is under a cable line, I keep it pruned 1-2x/yr (like my other European pears which always set nicely).
The tree is healthy, has great branching, but no fruit.
Just like you I have begun to suspect it is a tip bloomer.
Your post confirms my suspicion.

This is what I found on another forum:
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Sun, Mar 2, 08
Has anyone, anywhere had any luck with Warren pear? I have heard so many stories from homeowners and commercial growers that the darn things wont fruit. They are always very healthy in my area and always bloom well but dont seem to set fruit much. I am very convinced that it is pollen sterile but I have never heard of any leads as to what would be a suitible pollinator.
I have heard of some people who have apparently tried to artificially pollinate it but I don't know if this works.
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Mar 4, 08
I just planted one , too- on the claim. I read somewhere that it's the best pear variety for Texas. I put a 'Moonglow'(supposed to be a great pollinator) on one side and an 'Orient" on the other.
I wonder if decline in honeybees is why people are having trouble getting fruit there? This area has lots of pear trees in peoples' yards, which were all loaded last year.
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I've had Warren, grafted onto seedling P.communis rootstock, growing here for 10+ years. About 3 years ago, it produced three fruits.
However, the other dozen or so pears planted on that side of the pond with it have not yet reached sufficient maturity to bloom - I'm hopeful that they'll do so this year. Unfortunately - and perhaps doomingly, my Warren and Magness trees are at the ends of the new pear rows, as far away from the pears in the original section of the orchard as one can get.
Warren and Magness are reputedly two of the very best quality pears available, though I'm not so sure that I'm gonna be impressed, as I prefer a firm, crisp pear - and I don't mind grit cells(I like Keiffer!). The prevailing response I've been seeing recently on the NAFEX discussion list suggest that Warren really needs to be on a quince rootstock, or you'll be waiting forever for it to fruit.
Additionally, from the NAFEX list archives: "Just like Magness, flowers of Warren appear to produce no pollen or nectar. Therefore, pollinating bees have NO reason to visit its flowers. So...a good pollenizer (and there are many) needs to be very close to Warren or Magness trees for fruit set."
I've recently seen NAFEX pear enthusiasts suggesting that rather than have a dedicated Warren tree, that you graft a branch of Warren here and there into other pears that have the potential to serve as pollenizers - that way, if, say, the bees are swarming around your Harrow Delight, they'll probably visit the flowers on the branch of Warren you've fostered on there, whereas if you've got a free-standing Warren tree, it may get neglected.
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sept 2008
I had a warren pear I planted at least 12 years ago and I never got anything but two tiny pears. It never seemed to bloom so this summer I cut it down.
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I have decided that I am NOT waiting around for this tree anymore since my garden is too small for that luxury. I will cut it down and plant another fruit tree or shrub instead.

Hope this helps.

The bulk of the responses above are from me.

Again, Warren(and Magness, which resembles it in almost every way) are pollen-sterile, and also have little or no nectar, hence, they're not very appealing to pollenators(bees, etc.); hence the recommendations from many who've grown it NOT to have it as a free-standing tree, but rather as a branch grafted here and there in other fruiting pears - or, to graft other, more attractive varieties into your Warren tree.

Additionally, some Warren veterans have intimated that unless you're dealing with a Warren on quince rootstock, that you'll be waiting an inordinate time for it to ever begin flowering. It's a variety that really 'needs' the dwarfing effects of quince understock to force it into fruiting.

I agree that Warren has great branch structure, but I can't comment on tip-bearing - mine again has its typical 2 or 3 fruits this year, and I don't prune. At all. I'll try to ride out into the orchard this afternoon to gauge location of the fruits on the branches(if the hooved rats haven't eaten them).

Mrfignc, is your warren pear carrying the fruit still? Do you have a good set? Funny thing my Magness pear after 3 years in ground bloomed and set lots of pears this year. Unfortunatley a hail storm knocked them all off and caused fire blight to set in. It is on quince rootstock and that really seems to have made a diffrence. It is however a free standing tree with no pollinators grafted into it. It does have many other trees nearby to pollinate it and based on my records I think that an asian pear must have pollinated mine. I was so bummed about the hail damage but I was very encouraged about the fruit set and am probably going to add a Warren on quince to see what it does. My Magness really took a hit from the fb but I think it will recover.

Thanks,
Scape

My one and only Warren pear is on quince and is a tip bearer. The bees were usually reluctant to visit it even though a beehive is about 40 feet away, so several years ago, I started using bee scent, which works pretty good.