One Hand and Shield is the normal fundamental weapon chosen for Tanking. By using a shield you are able to block more damage and will unlock various passives and CP passives that will assist you in the ability to Tank and take damage.
Using 1H & Shield on both bars is very limiting and not advised at all since you only really need two One Hand and Shield abilities for almost all content it hold no extra benefit by using it on both bars. When you start out as a Tank using double One Hand and Shield is usually fine but it’s advised to switch to using an Ice Staff as soon as possible to open up your options on both useful abilities and group buffs and support.
Destruction Staff is extremely important on a Tank. The main reason this is used is because of the Elemental Blockade ability and the weapon glyphs. When you use a Staff, the weapon glyphs you use have double the value that they do on a 1 Handed weapon.
You should almost ALWAYS used an Infused Staff with Crusher Enchant – read more about the weapon traits and glyphs on those pages.
When you place your Blockade it will activate the Crusher debuff on the target that is closest to you. The enchant will stay on the enemy for 4 seconds and because the duration of Blockade is 12 seconds, even when you are on your front bar Blockade will automatically continue to proc the Crusher Enchant 3 times over the duration of its ability and you need to try and recast Blockade every 12 seconds to keep the Crusher enchant automatically reactivating itself on the target.
There are other abilities that you will need from the Destruction Staff skill line for various content such a Crushing Shock for Ranged Interrupting, Elemental Drain for debuffing and helping your Magicka DDs sustain via the Minor Magickasteal.
You should use a Frost Staff as they are the most useful.
Frost Staves: These are the most useful weapon to use as they offer you actual defence as a Tank and there is very little risk to using a Frost Staff compared to a One Hand and Shield. You get increased block mitigation, reduced block cost when using a Frost Staff for starters, and you have a unique debuff provided by a Frost Staff called Minor Brittle which increases the enemy critical damage received by 10% which is a big DPS boost for your group.
Some builds like to use the Tri-Focus passive but generally it’s advised not to use it until you are experienced with Tanking to utilise it properly. When using a double frost staff setup you might use it.
Minor Brittle Information | Elder Scrolls Online | Flames of Ambition
Using a Bow is a viable option in certain situations. It can be used anytime you are in a Magicka group composition who are not using Exploiter Passive CP and it would be used in situations where you are ranged Tanking such as vSS Ice.
As with the Destruction Staff, your Bow must be an Infused Crusher Bow 95% of the time. You could also use a Bow in a Medium Armor build to push some extra damage in score pushing teams. The main reason for using a Bow is because your Crusher Enchant will proc on the target that is in the very centre of your Endless Hail, compared with Elemental Blockade which causes your enchant to hit the target at the very front of the ability.
Both abilities have the same duration so both are viable options depending on the situation. Using a Bow would also be good to increase your DPS as an Off Tank or hybrid tank with the correct group setup. The Bow can also be useful for it’s ranged Interrupt with Venom Arrow and the passive Hasty Retreat which gives you Major Expedition when you Roll Dodge.
There is very minimal use for Dual Wield on a Tank. You could use it on a Off Tank or hybrid tank in situations where you receive low amounts of damage, if it works in your group and you are looking to do additional damage.
The healing output of a Tank is very low due to your low Spells Damage and Max Magicka so you usually would not use a Resto Staff. A Resto Staff can be a little useful for some of the passives and some healing abilities in 4-Man content where you are using 1 Tank and 3 DD’s, and in trials like vKA Hardmode it might be an option for the Off Tank to switch to a kind of 3rd Healer to help the group and Main Tank deal with all of the Incoming damage.
Some of the abilities you might use as a Tank are Combat Prayer for Minor Berserk and Minor Resolve, Siphon Spirit for Minor Lifesteal and Magickasteal and Healing Ward as well as the passives.