Well currently as we stand in beta right now its pretty much same build as normal tank but your stats points will be different.
Starting class:
Blade has been mentioned but most blade skills are of no use to a pure tank, so magic or knuckle? Magic to get charge lvl1+ and maybe later more skills? Knuckle, erm well maybe in future for sonic wave for ranged stun?
For all tank classes (except 2 hander tanks) everything in shield skill tree and knight skill tree is a must. Everyone of those skills at max are extremely useful.
Shield tree:
5 in top branch (just unlock the other skills), aspd boost with shield
.
Max. Both 2nd tier ones lvl10. One gives increases def and +hp (skill description doesnt say anything but it boost hp +1000hp ish at lvl10) shield bash is a must and at lvl10 (lvl5 doesnt cut it, fails too much) its a stun and allows breaks, very powerful. Use to break and to control when aggro is a problem or just spam. Cant stress how useful this is at lvl10!
The aegis skills in bottom half of the tree all very very useful, pick up 5 in each if possible max them. They are party wide buffs, use appropriately def one lowers mdef and vice versa.
Knight tree:
Assault is very powerful, it slows and knockbacks and can interupt those red skills on knockback. Lvl10 to be effective.
(As a side note: knife skill tree also has a slow skill, very powerful at lvl10 hits 5-6 times and slows at range, knife needed to be equipped though :/.)
Parry, well why not should be a must aswell. Doesnt work with guard but its an either or situation so if guard doesnt work parry might. Lvl10
Provoke: lvl10, effective and lowest mp cost.
(Skill after provoke, always forget the name :/) very useful as well with +aggro equipment.
(N.B. knight skill tree at the library says a sword is needed to use the skills. Currently thats NOT true assault, provoke and parry can be used/activate without a sword equipped, think of staff,knuckles etc.)
Survival:
the usual, pick up the max hp boost and mp (if you can, combat mp regen is more important than increasing max mp unless you have a cronic mp problem)
Support tree:
Probably struggling for skill points at this stage, mini heal is worth looking at. Only really effective at max, but the skill after it removing status effects is worth investing into removing that poison, ignite etc.
An update/official release increasing lvl cap and unlocking new skills is kinda needed to advance this further.
The original poster, obviously, played alpha. A lot has changed and will be changed from alpha, hoping this long post helps for us in beta right now
Regarding elemental swords, not available yet, they are listed under customise equipment but need 100 potential, even with -ve stats it no where near
. Increasing lvl cap does very little for this sadly (lvl70 adds +6 potential assuming +2 stat points per lvl) an expansion of smith skills and stats added is needed.