no, being 7th itself isn't particularly impressive, but 3rd, 4th, 5th - those are pretty impressive. That said, doing it once or twice is not very special. Doing it 11 times - that is awesome. Horton has always been very underrated offensively.
Horton's ten best seasons, expressed as a percentage of the #2-scoring defenseman:
84, 83, 81, 80, 80, 76, 71, 71, 67, 64.
The same for MacInnis:
110, 109, 101, 100, 100, 99, 94, 92, 90, 86.
MacInnis' offense was about 30% better than Horton's. Was his defensive ability within 30%? When you consider their entire careers? I would say it definitely wasn't.
Horton might be a tad overrated and MacInnis a bit underrated, but I'd still take Tim over Al.