The steam wand enuf power? Im not familiar with breville. Mayb need times to practise. Watch more youtube.

Extraction time is from the moment the water hits the coffee. I would say it looks good overall just need some work on the pour

Foam consistency will also affect your latte art. Even if you pour the same way but the thickness of the milk if not the same will give u bad results too

What's your dosing parameters? single/double?
If you're doing a single shot latte, usually hard to tell if there's any extraction problems. A double shot latte (at least) or straight espresso is best to check on result

Couple of people are selling on Lelong, but the ones I got from them have mostly
INACCURATE measurements! It may or may not matter to you...

You could try weight measuring of shots instead of volumetric. Also, since the thickness of crema depends on the age of the bean, it can sometimes throw you off
I find a 16g coffee/32g espresso much more balanced and sweet than a 16g coffee/60ml output (i could tweak to pull 55ml but try doing that manually by eye  )

I use a lab glass beaker .... 150ml. Cheap (RM12 each plus delivery charges), strong (heat-resistant borosilicate glass) accurate measurements (if you are targetting where the marks lie), and so very cool. The only thing about the 150ml is that it is slightly too tall for the Poemia, so have to tilt it slightly when putting in under the portafilter... should have gone for the 100ml.

Oh, I meant measuring realtime

Volume measurement is actually supposed to include creama too so this will be considered slightly of a lungo shot 
Preinfusion + brew time = 29sec is perfectly fine already, shouldn't need to tweak on dose and grind size further.
Ultimately, how's the taste?

Feels a little fast to me. Grind a notch finer or tamp slightly harder
How about the body? Does it taste watery or thin?

While chasing perfection is kinda fun but what really matters is that end of the day you enjoy the coffee. So if you like the taste, go for it
Can't really help much unless you have another person drink and feedback

What grinder are you using again?

Up dose...

Yes...Stale beans run fast. Grind too fine gets bitter. Milk reduces the bitterness....so maybe that's why it tastes OK. I find that the best is up dose. Tamping won't help as you have found out.

Wow, you guys are good la... after almost 2 years on my BES920, my latte art still crap, can't get a decent rosetta, most of the time just looks like volcano eruption, nuclear bomb or elephant head 

Do you guys steam according to temperature? im doing it religiously at 60 Celsius, but most of the time the froth seems to be thicker, and can't pour so many fine lines...

Usually i start with 200ml of milk, by 60 C it will be around 400ml... a bit too much air?

Thanks dwRK, am testing out the 1-2cm increase, letting very little air in and more swirls, but like what you said, its challenging to get art as i utilize every drop of milk..
And I'm using a keepcup instead of a ceramic kind of cup. which I think is one of the reasons perhaps harder to tilt and do art..
So I think aim is still to get maybe around 2cm or around 3/4 jug at 60°C, then try my rosetta again.. maybe start with heart easier 
20% lesser air? Im testing the approach to let in lesser air now, see how the art goes.