Ok we have had Titans for a while now, and to be honest they are a bit on the overpowered side. Now they are legendaries and are supposed to be on the strong side so I do get and accept that. However they can be extremely frustrating dealing with multiple copies of them (looking at you priests) if your opponent builds their deck with copiers. Amun’Thul is easily the most abusable Titan in game and is massively unfun when dealing with up to 6 extra copies of him in your opponent’s hand, not counting minions that can copy him on the battlefield (though they only have abilities not used).
The primary change I feel that they should have is that their abilities can be used only once per game per ability. This should be possible as there are cards (namely Timewinder Zarimi and Hearth Stonebrew) who’s abilities can be used only once per game no matter how many copies you might have of them or even by bouncing them back into your hand or deck. This would keep them much more balanced as there is a card (Shattered Reflections) already ingame that specifically says that it can not copy Titans which suggests that Titans were initially supposed to be uncopyable. With this change should you get a copy of a Titan you already played, any abilities it used would be blocked out and unusable on the new copy.
An option that could also be done is that Titans, regardless of other cards, could be changed to be uncopyable by any means.
The second change is actually more of a playability factor in that you SHOULD be able to attack with them if you do not want to use one of their abilities, more often because you do not feel like it is the right time to use said ability or would normally be unable to make use of it. This of course runs the risk that your opponent could kill your Titan before you use it’s abilities, but that is the risk you take to attack rather then use an ability.
As an example Aggramar, the Avenger’s powers require that you have a weapon equipped (as it’s battlecry you equip a 3/3 weapon). However if you play him and your opponent destroys your weapon, he becomes useless until you equip a new one or waste a power or two THEN he can attack. With this change he (or any other Titan) can attack rather then use an ability either going for face or hitting an enemy minion of your choice.