By a lot of people, yes it is! It also helps you, assuming you’re not vying for a PvP Leaderboard position.
Setting an easy defence, and/or one that helps fulfill the weekly event, makes you a much more attractive option to attack. When someone beats you, the next time you see them in your 3 PvP choices, they will show up as a ‘Revenge’ battle, which gives you (aside from +3 Glory) double the gold reward if you beat them. This doesn’t show up in the post-battle Rewards screen, but if you check your gold before and after, it will be there.
If you are vying for a PvP Leaderboard position, it’s understandable to try to set a hard defence, so that you don’t lose as many PvP points – as you said 
.
If you pop in to Global 001 at the start of the week, you may often see people reminding each other to set up a defence that’s helpful for the week’s Event - e.g. typically 4x Drake Riders have been used a lot for Brown events like this one, as they spawn another Brown unit on death, but a lot of people have started asking each other to not set this one as the battle takes longer for the same rewards, and can be kind of annoying. On the other hand, it’s a guaranteed 8 Event Points in an arena where not everyone sets a helpful defence.
Another couple of tips would be:
- Try to make your defence unique, so that it has a greater chance of appearing to other players due to recent changes in matchmaking (a single different troop, class or banner will do – not sure about order)
- Try to use troops that give you the highest team score possible, so that you are attacked by higher level players (if that’s what you want). This means using your highest levelled and most traited troops. Note that a Common troop ascended to Mythic gives the same amount of points to your score as a Base Mythic troop.
E.g., this is my defence (no one copy! 
):
N.B.:
Other relevant threads:
- Weekly PvP Event Defense
- Devs please support weekly events
- PvP defense question
- PvP defence: weak team or Firebomb team?