Need help to choice a viable boss killing class

[Fitsu]

This highly deepends on ure available funds. Some of the top/most common builds are:

Fire Sorc (Expensive, heart of hell, azmo armor, golem chants, no real other fire builds so can't make multiple characters with same gear)
WW Barb/Phys Bowazon/Phys Summoner Necro (Both semi-expensive.. The usual phys stuff: titans, arkains, relic.. Nice thing about this route is apart from weapon they both wear effectively the same gear and I'm sure there's other viable phys builds out there)
WC Barb/Spear Necro (Nice thing about magic is u can get it going on a fairly cheap setup... Vastly cheaper than any other build and then move towards the more expensive items such as reapers.)
Vengence/Lite Zeal pala (Vengence just needs TF to get going which is actually pretty cheap atm as the lightning aura isn't so important but Lite Zeal needs Corr SS/Lite Neph so is very expensive)
Fire Druid (Hella tanky but overall pretty weak imo)

I have no idea how to build a WW Sin so can't comment on that... I actually don't think I've seen one this ladder. Barb seems to be stronger with WW now.

Those are the most common builds. Unfortuently any build requires you to stack -element to a point where you can actually deal damage and the content is fairly hard to begin with especially with the new-style DPS checks so the amount of viable builds is imo quite limited... But this tends to be the trade-off, the more difficult the content is the less viable builds there are. It's just the way of things.