While there are several thoughts in market about how good Design skills can be gained - Where some people have opinion that Design can be only learned from Experience while other may talk about Study as Tool or perhaps availability of Case Study can fasten the process.
On the flip side some Expert Level Certification like CCIE usually doesn't focus on Design side of protocol but rather feature set. For example the Scenario I shown above - It's very easy to trick a CCIE with even this small OSPF setup by asking if they see any design issues with this design. And Most likely the answer is going to be - "No"
Now lets take a look at Design issue with even this small setup:
Lets say R1's Loopback wants to Talk to R5's Loopback. Let's see what Traceroute has to say about path being followed:
R3#traceroute 18.104.22.168 source loopback0
Type escape sequence to abort.
Tracing the route to 22.214.171.124
1 126.96.36.199 40 msec 100 msec 48 msec
2 188.8.131.52 160 msec 48 msec 52 msec
Looks good so far as we are talking the shortest path to reach the destination.
Lets review R1's routing table which is next hop in this case:
R1#sh ip route 184.108.40.206
Routing entry for 220.127.116.11/32
Known via "ospf 1", distance 110, metric 2, type intra area
Last update from 18.104.22.168 on FastEthernet1/0, 00:01:04 ago
Routing Descriptor Blocks:
* 22.214.171.124, from 126.96.36.199, 00:01:04 ago, via FastEthernet1/0
Route metric is 2, traffic share count is 1
Still being CCIE and looking at the output above, you might not have observed design issue here.
Let's bring the link down between R1-R5:
*Mar 1 00:39:10.651: %OSPF-5-ADJCHG: Process 1, Nbr 188.8.131.52 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
And now let's run the Traceroute again to see if we are are following the shortest path as shown in diagram below: