Sixteen is a big level for Templars, with the addition of 1 passive ability, 2 upgraded skills, and 2 brand-new ones. Boost Shield Defense improves your blocking. Rage and Weakening Severe Blow both get better, while Provoking Severe Blow and Shining Slash are added to your arsenal.
Now that you have two additional offensive abilities, you can try switching to a greatsword while soloing and ignoring the abilities that require a shield. You will undoubtedly burn through mobs faster, but you may find the trade off of increased incoming damage is not to your liking. You can also try utilizing the Switch Weapon ability (hot-keyed or clicked from your skill bar), leading off with a greatsword through the opening offensive moves, and then switching quickly to your 1h and shield in order to take advantage of Shield Defense. If you are tanking for a group, however, you should always have on your one-handed sword (or mace) and shield. Your healer will thank you for it.
Level 19 brings only one upgraded ability, and a new offensive chain skill in Wrath Strike. This one is new, however, in that also chains from a chain skill. You've seen how using Ferocious Strike gives you a choice between Rage and Robust Blow, but Robust Blow, when chosen, now will proc Wrath Strike.