1. no dual wield
2. no high-damage direct-damage skills like pincer, flurry, drum
3. no passive damage procs (riposte, concealed)

Its strengths:

1. very good melee defence, it can turn giants from face-tankers into excellent tanks.
2. slice bleeding with high strength and the edge (swath of destruction) is almost as good as dagger artery bleeding. Mostly relevant in lowbie PK.
3. charge set for great PK defence against melee types: spamming flee in panic might actually not get you killed and run the killer off instead.
4. cutoff for great ganging, especially if your allies tend to be bad at lag and good at landing curses (paladins, shamans, necromancers).
5. polearms very seldom trigger riposte or concealed from your opponent.
6. polearms are probably the hardest weapon to parry and they don't totally suck against dodge: it would be a bit OP if you could dual wield them.

How to maximize strengths and cover weaknesses:

1. adding offence: villager scout's critical hit skill is very strong at covering polearm spec's weakness. That said, village scout is probably not an ideal powergamer build.
2. adding offence: spamming lots of progging items (prayer beads, thunderlance, etc.) is not a terrible idea. Because of prayer beads, I think good-aligned bash specialist is a good choice.
3. being a good gang partner: Imperial, Fortress.

Particularly I want to point out Maran storm giant (or maybe even dwarf). A skilled Maran giant pole spec with Greeting and cry of deliverance could turn a fellow Maran into a walking death trap against solo enemies, or even multiple enemies if fellow Maran is a high-power low-lag type (Maran paladins like these are fairly common).

One of the weaknesses of cry of deliverance is that the enemy can flee immediately if the lag is not perfectly timed.. timing like that without voice comms would be nigh impossible.