Ya... 811 is one of them. Turn right out of INT then going past
the industrial estate, crosses AVE 2 and heads to Chong Pang. After
which, it turns left opposite Yishun MRT Station (instead of right)
into AVE 2 and turns right, past the industrial estate, by which
turning out after the CC and finally reaches the terminal.
Waste of time. 
811E still ok.
Actually right, if you want to take feeder/intratown into some
parts of Yishun very easy. Yishun is labelled into 3 sections,
Central, East and South.
800 - East crossover to Central (N2
N7)
804 - East (N2 & N3)
806 - Central (N4)
811 - East (N1, N2, N3 and industrial estate)
811E - South (N8 & some parts of N6)
812 - Central (N6)
812E - East (N1 & N7)
With this in mind, you won't take the wrong service. 
Actually this reminds me of Express 520 which started from Yishun
last time. Instead of following other trunk services that are
heading towards City by using AVE 2 and Lentor AVE, Express 520
loops around Chong Pang and then turns right at Khatib MRT Station,
which was, quite redundant because it was a waste of time.
Speaking of 800, it's also quite a loopabout service. Turning into
Yishun CC outside INT it goes around N2 and then crosses AVE 2 into
Chong Pang area and goes around N7. But then it passes by Chong
Pang area again and back into N2, before turning out of the CC into
the interchange. That's why many people living around the Chong
Pang area chose to take 812 to the interchange because it was very
direct. Yishun Ring Road
AVE 2,
excluding waiting time it only takes 5 minutes to get to the
interchange. Whereas for 800, it takes around 15 - 17 minutes. I've
seen many times 800 came first then followed by 812, 812 reached
the terminal first. 
So, if you are going to the main areas of Yishun, here's my
advice:
South: 811 (Only takes 5 minutes to get to opp. NTUC Block
849)
East: 812 (7 mintues to get to opp. Chong Pang CC and 10 minutes to
N7 area compared with 20 - 25 minutes to N7 for 800.)
Central: 812 for N6 area after SAFRA, 806 for those in N4 and a bit
of N3 area.